So I have an old pc from the year 2011, it would be possible on it to play Minecraft with about 30Fps if so how?
Sure, this is possible, I play on my laptop from 2010 and have 50 fps.
That can't be said, if you do not at least processor, video card, memory, possibly motherboard and hard drive call.
A PC from 2011 can run the game easily or just not, depends on the equipment.
Depends on.
eg i5-2400
GTX 750ti
8 GB RAM
HDD
Yes, that works very well and even Fortnite
But you can't say that flat because there are MANY 2011er models and many Konstelattionen