I have Microsoft paint but not paint.net because it's too laggy for me.
Paint.NET shouldn't be laggy, it's not even 3D.
Try GIMP then?
And also, you could try to get friends, and play around with them, or you can join race servers, deathrun servers, challenge servers, and the many more types of server out there that don't necessarily requires you to fight.
But please be warned, it's true, you can build because it's your right and if you like it and it's fun for you there's no reason to take words of your brain and just do it out of your hearts.
As for going to build-specific servers, please be warned some people want their server more... 'perfect', or they may be just harsh, so you could get your build deleted, however freebuilds usually (or shouldn't) contain such rules.
And just a few suggestions related to building: Don't use small pieces, try to use bigger walls instead of 1x1x5's and so on, people will classify it as spam and remove it, sometimes even on freebuilds. That is, unless the host builds the same way as you.
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