I will be saying sorry first for my English since English isn't my first language...

So, the problem is I had download font named "Unek" and used it as logo for non profit instagram account...
But since I have expand it to website and will be a profit thing, I'm going to buy that font... But the only option I have is just "donate"...
If I do donate, is it same as buy the font with whatever price I give to the author? Or not?

Go to https://www.dafont.com/profile.php?user=682922 and click on "Send a private message"

Tell the font author how are you going to use the font and then ask him how much do you have to pay for such a usage. It is only him who could say how much the commercial license for his fonts would be.

If you prefer to contact the author by email, click on "Donate to author" and it will show you his email address. That is just a way to get his email address and not a suggestion to make a donation.

Talk to the font author first.

Allright, thanks a lot for answering...