How modify list values from a Pickervalue

I have a list which is already containing different values. For each List postitions I have made a button which leads to a sheet View which contains a Picker to change the value of minutes and seconds. When I open up this Sheet view it will present for each Listrow the right amount, but if I change it, it will not be passed to the row once i close the sheetview.

It will also show me the Warning on both picker values "$minutes" and "$seconds"

What am I doing wrong? What is missing?

import SwiftUI

struct LevelData: Identifiable {
    let id = UUID()
    let imageName: String
    let title: String
    @State var minutes: Int
    @State var seconds: Int
}

struct IntervalListView: View {
    
    static let Level4Interval1Medium = [
    LevelData(imageName: "BreatheSymbol", title: "Breathe", minutes: 2, seconds: 00),
    LevelData(imageName: "HoldsSymbol", title: "Hold", minutes: 2, seconds: 00),
    LevelData(imageName: "BreatheSymbol", title: "Breathe", minutes: 1, seconds: 45),
    LevelData(imageName: "HoldsSymbol", title: "Hold", minutes: 2, seconds: 00),
    ]
    
    @State var LevelDatas: [LevelData] = Level4Interval1Medium
    @State private var showingSheet = false
    
   
    
    var body: some View {
        
        ZStack {
            VStack {
                
                List {
                    Section{
                       
                        HStack {
                            Text("14 min")
                            
                            
                                Spacer()
                            NavigationLink("Start", destination: SomeView())
                                .frame(width: 60.0)
                                .foregroundColor(/*@START_MENU_TOKEN@*/.blue/*@END_MENU_TOKEN@*/)
                            Spacer()
                            Image("Save")
                                
                        }.listRowBackground(Color(.secondarySystemBackground))
                    }
                    
                    ForEach(LevelDatas,id: \.id) {
                        item in
                        
                        HStack {
                        
                            Button("") {
                                showingSheet.toggle()
                            }.sheet(isPresented: $showingSheet) {
                                ZStack{
                                    
                                    VStack(spacing: 20) {
                                        Text("Set \(item.title) Time")
                                            .bold().padding()
                                            .frame(maxWidth: .infinity)
                                            .background(Color(#colorLiteral(red: 0, green: 0.22, blue: 0.36, alpha: 1)))
                                            .foregroundColor(Color.white)
Spacer()
                                        HStack {
                                            
                                            VStack {
                                                Picker("", selection: item.$minutes){
                                                    ForEach(0..<9, id: \.self) { i in
                                                        Text("\(i) min").padding(.leading, 40.0).tag(i)
                                                    }
                                                }
                                                
                                                .pickerStyle(WheelPickerStyle())
                                                
                                                .clipped()
                                            }

                                            VStack {
                                                Picker("", selection: item.$seconds){
                                                    ForEach(0..<60, id: \.self) { i in
                                                        
                                                        Text("\(i) sec").padding(.trailing, 40.0).tag(i)
                                                    }
                                                }
                                                .pickerStyle(WheelPickerStyle())
                                                
                                                .clipped()
                                            }
                                            
                                        }

                                        Spacer()

                                        Button(action: {
                                            self.showingSheet = false
                                        }){
                                            Text("Done")
                                        } .padding()
                                    }
                                    
                                } .presentationDetents([.medium, .large])
                            }
                            
                             
                            Image(item.imageName)
                                
                            Text (item.title)
                                .font(.title2)
                                .fontWeight(.semibold)
                            Spacer()
                            Text("\(item.minutes):\(item.seconds < 10 ? "0" : "")\(item.seconds)")
                                .padding(.trailing, 10.0)
                            
                      
                        }
                        
                    }.onDelete { indexSet in
                        LevelDatas.remove(atOffsets: indexSet)
                    }
                    
                    
                }.navigationTitle("Overview Intervals")
                    .toolbar {
                        EditButton()
                    }
                    
                
            }
        }
        
        
        
    }
    
    struct IntervalListView_Previews: PreviewProvider {
        static var previews: some View {
            IntervalListView()
        }
    }
}