OK, i tried it both on steam and GOG, but paysafe card doesn't work for me as in It doesn't even load the page, where i am supposed to pay.
Is it like this for everyone or its just problem at my end?

Try a different browser with no add-ons and default settings.

Tried mozilla, Chrome and app too, but the same result.

Contact Paysafecard support.
https://www.paysafecard.com/en/support/contact-us/

I just bought a game and could pay for it. So it works on my end.
Using any specific older os?

Well, no.
The thing is that no matter what computer i use, it just doesn't load.
Steam doesn't load and GOG shows error message.

If that's happening on different computers with different configurations and various sites, must have to do with the network, your router or ISP or something in between.

If it happens on different computers, with different browsers and even on different sites that pretty much rules out the browser and the computer. it must be one of the following:

1) There is a problem with PaySafeCard. Not impossible, but improbable since other people can use it without problem.
2) Your ISP or country is blocking PaySafeCard because they think it is nefarious.
3) You use the same antivirus on all your computers. Most antivirus products nowadays also have some form of internet protection which blocks nefarious sites and your antivirus thinks PaySafeCard should be blocked.
4) You use the same ad- or scriptblocking addons on all computers and browsers and one of them is interfering with PaySafeCard. Are you sure you have switched off all addons?

Okay, it turned out that i needed only to restart wi- fi.
thank you all for help.

You mean router, yes? Sounds like you have dynamic IP and the one you used was blocked or banned by PaySafe.