Problems with creating a postgresql trigger function to create a modified entry for every insert statement

So my first question here on SO, let me describe the setup: I have a postgressql database (version 12) with a table guilds (containing an internal guild_id and a few other informations). The guild_id is used as foreign key for many other tables like a teams table. Now if a team is inserted in teams for another guild then the guild with the guild_id = 1, I want a trigger function to create the same team entry, but now with a modified guild_id (should be now 1).

Definition of the relevant things I have atm:

create table if not exists bot.guilds
(
    guild_id         bigserial not null
        constraint guilds_pk
            primary key,
    guild_dc_id      bigint    not null,
);
create table if not exists bot.teams
(
    team_id       bigserial   not null
        constraint teams_pk
            primary key,
    guild_id      bigserial      not null
        constraint teams_guilds_guild_id_fk
            references bot.guilds
            on delete cascade,
    team_name     varchar(20) not null,
    team_nickname varchar(10) not null
);

alter table bot.teams
    owner to postgres;

create unique index if not exists teams_guild_id_team_name_uindex
    on bot.teams (guild_id, team_name);

create unique index if not exists teams_guild_id_team_nickname_uindex
    on bot.teams (guild_id, team_nickname);

create function duplicate_teams() returns trigger
    language plpgsql
as
$$
BEGIN
    INSERT INTO bot.teams VALUES(1,NEW."team_name",NEW."team_nickname");
RETURN NEW;
END;
$$;

create trigger duplicate_team
    after insert
    on bot.teams
    for each row
execute procedure bot.duplicate_teams();

If I try now to insert a new row in teams (INSERT INTO bot.teams ("guild_id", "team_name", "team_nickname")VALUES (14, 'test2', 'test2');), I get the following error message (orginial german, translated by me to english):

[42804] ERROR: Column »guild_id« has type integer, but the expression has the type character varying
HINT: You have to rewrite the expression or cast the value.
WITH: PL/pgSQL-function duplicate_teams() row 3 in SQL-expressions

After execution the orgininal insert statement isn't in the table neither the copy. I tried to cast the values for the guild id to serial, integer, bigserial.. but everytime the same error. I'm confused by the error message part with "has the type character varying".

So my questions are:

1. Is my understanding correct, that the error is caused by the trigger? and due to the error in the trigger the original insert statement doesnt work too?
2. Why is the type varing even with a cast?
3. Where is the error in the code?

I tried to search for the problem, but found nothing helpfull. Any hints are welcome. Thank you for your help!

EDIT: The answer from @Lukas Thaler works, but now I get a new error:

[23505] ERROR: doubled key value violates unique-constraint »teams_guild_id_team_name_uindex«
Detail: Key»(guild_id, team_name)=(1, test3)« exists already.
WHERE: SQL-Statement»INSERT INTO bot.teams(guild_id, team_name, team_nickname)  VALUES(1,NEW."team_name",NEW."team_nickname")«
PL/pgSQL-Function duplicate_teams() row 3 in SQL-Statement
SQL-Statment »INSERT INTO bot.teams(guild_id, team_name, team_nickname)  VALUES(1,NEW."team_name",NEW."team_nickname")«
PL/pgSQL-Function duplicate_teams() row 3 in SQL-Statement

But the table only contains only "3,11,TeamUtils,TU"...