GitLab.com slow while logged in

Hello there.
I’m having issues accessing the web interface of GitLab.com while logged in.

While not being logged in, pages load in less than a second.
However, when I’m logged in (through Github, if it matters), I get a response from the server after ~4000ms.

What should I do?
(I’m using Firefox 65 on Linux, with uBlock Origin [issue still occurs when uBlock is disabled])

Just F your internet

Literally this type of problem happen due to rapid increase of junk files. The same problems happened with me too. To clear junk files, I tried to download system mechanic and I could do that. Now my computer is working great.