Create view oracle sql

I am making a database with tv-shows and users. These users can follow each other and are saved in the database by an UserID. Now I wan't to create a view with the names of the users instead of the UserID's. --Drop all tables.

DROP TABLE Series CASCADE CONSTRAINTS;
DROP TABLE User1 CASCADE CONSTRAINTS;
DROP TABLE FollowingSeries CASCADE CONSTRAINTS;
DROP TABLE FollowingUser CASCADE CONSTRAINTS;
DROP TABLE Episode CASCADE CONSTRAINTS;
DROP TABLE Watched CASCADE CONSTRAINTS;
DROP VIEW Test CASCADE CONSTRAINTS;

--Create all tables.
CREATE TABLE Series
(   SeriesID NUMBER(5) primary key,
    Name VARCHAR2(100) NOT NULL,
    Status VARCHAR2(20),
    Premiered DATE,
    Genre VARCHAR2(100),
    Country VARCHAR2(100),
    Network VARCHAR2(100),
    Runtime VARCHAR2(25)
);

CREATE TABLE User1(
  UserID NUMBER(5) primary key,
  Username VARCHAR2(100) NOT NULL,
    Country varchar2(100),
    Gender VARCHAR2(10),
    Birthday VARCHAR2(100),
    About_me VARCHAR2(300),
    Password VARCHAR2(100) NOT NULL
);

CREATE TABLE FollowingSeries (
    UserID NUMBER(5) NOT NULL,
    SeriesID NUMBER(5) NOT NULL,
    Ignore1 CHAR(1) DEFAULT 0,
    constraint FollowingS_pk primary key(UserID, SeriesID),
    constraint FollowingS_fk1 foreign key(UserID) REFERENCES User1(UserID),
    constraint FollowingS_fk2 foreign key(SeriesID) REFERENCES Series(SeriesID)
);

CREATE TABLE FollowingUser (
    UserID1 NUMBER(5) NOT NULL,
    UserID2 NUMBER(5) NOT NULL,
    constraint FollowingU_pk primary key(UserID1, UserID2),
    constraint FollowingU_fk1 foreign key(UserID1) REFERENCES User1(UserID) ON DELETE SET NULL,
    constraint FollowingU_fk2 foreign key(UserID2) REFERENCES User1(UserID) ON DELETE SET NULL
);

CREATE TABLE Episode(
    SeriesID NUMBER(5) NOT NULL,
    Season NUMBER(2) NOT NULL,
    Episode NUMBER(2) NOT NULL,
    Name varchar2(100) NOT NULL,
    Airdate DATE,
    Summary varchar2(1500),
    constraint episode_pk primary key(SeriesID, Season, Episode),
    constraint episode_fk foreign key(SeriesID) REFERENCES Series(SeriesID) ON DELETE SET NULL
);

CREATE TABLE Watched(
    UserID NUMBER(5) NOT NULL,
    SeriesID NUMBER(5) NOT NULL,
    Season NUMBER(2) NOT NULL,
    Episode NUMBER(2) NOT NULL,
    constraint watched_pk primary key(UserID, SeriesID, Season, Episode),
    constraint watched_fk1 foreign key(UserID) REFERENCES User1(UserID),
    constraint watched_fk4 foreign key(SeriesID, Season, Episode) REFERENCES Episode(SeriesID, Season, Episode)
);



--Add users.
INSERT INTO User1 VALUES (1, 'StefPhilipsen', 'Netherlands', 'Male', TO_DATE('02-01-1994','DD-MM-YYYY'), 'Ik ben Stef', 'abcd1234');
INSERT INTO User1 VALUES (2, 'Dorothy142', 'America', 'Female', TO_DATE('01-10-1963','DD-MM-YYYY'), 'I love mountainbiking', 'Oow6sai4Ie');
INSERT INTO User1 VALUES (3, 'Rudo12', 'England', 'Male', TO_DATE('05-6-1985','DD-MM-YYYY'), 'I watched Breaking Bad and a lot more', 'Oph9Ge2yai');
INSERT INTO User1 VALUES (4, 'JohnSmith', 'England', 'Male', TO_DATE('27-9-1945','DD-MM-YYYY'), 'I like potatoes.', 'phiShaip0c');
INSERT INTO User1 VALUES (5, 'EulaWGibson', 'America', 'Female', TO_DATE('12-8-1990','DD-MM-YYYY'), 'I''m Eula. I live in massachusetts and I''m happily married with my husband Hank.', 'EiM5wii2am8');
INSERT INTO User1 VALUES (6, 'Pedro', 'Spain', 'Male', TO_DATE('12-10-1945','DD-MM-YYYY'), 'I love watching Arrow.', 'Gith0yaiw');
INSERT INTO User1 VALUES (7, 'TravisC', 'England', 'Male', TO_DATE('12-7-1970','DD-MM-YYYY'), 'My favorite TV-shows are Modern Family and Dexter.', 'gie9aiPh2Ii');
INSERT INTO User1 VALUES (8, 'DonellaScott', 'America', 'Female', TO_DATE('31-1-1996','DD-MM-YYYY'), 'Living the life.', 'Gued1996');

--Who follows which series.
INSERT INTO FollowingSeries(UserID, SeriesID) VALUES (1,1);
INSERT INTO FollowingSeries(UserID, SeriesID) VALUES (1,2);
INSERT INTO FollowingSeries(UserID, SeriesID) VALUES (1,3);
INSERT INTO FollowingSeries VALUES (1,4,1);

--Who follows who.
INSERT INTO FollowingUser VALUES(1,2);
INSERT INTO FollowingUser VALUES (2,3);
INSERT INTO FollowingUser VALUES (3,4);
INSERT INTO FollowingUser VALUES (1,3);
INSERT INTO FollowingUser VALUES (5,8);
INSERT INTO FollowingUser VALUES (5,6);
INSERT INTO FollowingUser VALUES (6,5);

-- Which episodes are watched by whom.
INSERT INTO Watched VALUES(1, 4, 1, 1);
INSERT INTO Watched VALUES(1, 4, 1, 2);
INSERT INTO Watched VALUES(1, 4, 1, 3);
INSERT INTO Watched VALUES(1, 4, 1, 4);
INSERT INTO Watched VALUES(1, 4, 1, 5);
INSERT INTO Watched VALUES(1, 4, 1, 6);
INSERT INTO Watched VALUES(1, 4, 1, 7);

This is what I tried but then I get an error message

--Create view
    CREATE VIEW follownaam AS
    SELECT followerUser.Username AS Follower, followingUser.Username AS Following
    FROM FollowingUser AS fu
        INNER JOIN User1 followerUser ON(fu.UserID1 = followerUser.Username)
        INNER JOIN User1 followingUser ON(fu.UserID2 = followingUser.Username)
        WHERE fu.UserID1 = 1;

[Err] ORA-00911: invalid character

The table I have exists of 2 UserID's. But now I want exactly the same table, but this view must contain the Usernames of these UserID's.