Can I turn a Dell optiplex 7010 with Intel i5 3470 3.2 GHz with 16 GB RAM and 1 TB hdd into a gaming pc?

As already described above, please give a few tips I would like to spend under 100 euro for a graphics card

would like to play esport titles like fortnite csgo.

https://systemanforderungen.com/spiel/fortnite the requirements for Fortnite

The https://systemanforderungen.com/spiel/counter-strike-global-offensive for CS: GO

Maybe ne 700 or 900 GTX could help, but whether it really brings something. You should try it

According to the site with a GTX960, Fortnite should be very playable…

Will be difficult with a 275W power supply without PCIe power supply… The CPU doesn't leave much room anyway.

A GTX1650 4GB is feasible, however.

Price is around 135 euro.

Or a used GTX 1050ti 4GB. Is around 80 euro