With Mini PC?

I have a question and whether I can play fluently with the ACEPC t11 Minecraft and fortnite

Is nothing

Minecraft probably. But only in older versions like 1.5 or older

Fortnite I think is not possible

Otherwise expand the PC with more RAM or better graphics card

And how can I extend it with a graphics card?

I recommend at a PC shop

You can also do it yourself (at your own risk)

Preferably an external graphics card (ie connect with USB cable)