I need help because i cannot install games. Every time i try to download them, it asks me for the password and even if i write the correct one it does not allaw me to download them even if i have bought them.
Do you have any suggestion?

Could you be give more detailed info? Was it the website or GOG Galaxy? Did you try to clear browser cache or reinstall Galaxy (with cleaning its leftover files and register keys)?

Sounds like this problem:
Strange issue with Login when trying to post reviews and add to wish list

An infinite login loop is typically caused by blocking content or cookies. The first thing to try is a different browser or GOG Galaxy. But as you can see in the above thread, all obvious troubleshooting steps have been tried in that case and the problem persists.

The only additional suggestions I have is to disable IPv6, set DNS to Cloudflare ("Setup on PC" section near the bottom), and restart the system. If that doesn't help, feel free to revert the changes.

yes but the problem still

In addition to the hints above also try to create a exception in your firewall. Certain firewalls have caused problems with GOG scripts since the latest change in the server structure.

Hmmm..... Sounds like clearing the cache and restarting the computer SHOULD do it....

Ooooooooooooooo... help me! Let us share this hope...

Sounds like you have a serious browser problem. Perhaps it's time to cleanly reinstall it?

I'm gonna be that guy.

Did you contact support?

Close all your browser windows and tabs, restart and clear all cache + cookies + other stuff from the "beginning of time".

Open your browser and set it to default settings and try again.
Different browsers have different naming for just that. For example in Opera browser it's called "Reset settings / Restore settings to their original defaults"

Check your HDD/SDD for malware & viruses with antivirus/firewall software. Preferably on a clean install system: from a different HDD/SDD or even on another PC.

As a temporary workaround for playing / installing your games try using GOG Galaxy launcher.
https://www.gog.com/galaxy