tlmgr doesn't work

[Torbjörn Svensson Diaz]

Hello!

I have trouble using tlmgr.

user at user-desktop:~/Documents/Programming/LaTex$ sudo tlmgr update --self
(running on Debian, switching to user mode!)
Cannot determine type of tlpdb from /home/user/texmf!
cannot setup TLPDB in /home/user/texmf at /usr/bin/tlmgr line 6424.

The same result appears when I try to install packages. I run Ubuntu 
18.04.6 LTS.

What am I to do? Can someone please help me?

-- 

Torbjörn Svensson Diaz