Gaming PC suddenly has fewer fps?

I have the problem that my PC suddenly creates fewer fps and sometimes drops below 20 with Fortnite, for example, but I don't know why. Not even in 720p low settings in Fortnite it manages a constant 120 fps and also in this resolution I have strong fps drops below 20.

My specs:

I5 4590 gtx 970 4gb and 8gb Ram (2x4gb).

I think the I5 bottlenecks, and Fortnite is also badly optimized as far as the drops are concerned.

But that wasn't as bad as it is now. I had better fps even in 1080p.

Then maybe the processor or graphics card is defective or overheating. When has this started? After an update or did you install something new? E.g. Driver for the graphics card?

Sounds like a heat problem. If the processor gets too hot, it clocks down & the FPS drop. Have a look at the temperatures?

Ne did not install anything and there was no update.

Around 60

Degree

That's a decent temperature - so it can be excluded as a source of error. What about the driver? Are they up to date? Next I have to ask what kind of playback medium you have? Can it do 120Hz?

That's a decent temperature - so it can be excluded as a source of error. What about the driver? Are they up to date? Next I have to ask what kind of playback medium you have? Can it do 120Hz?

How can I look that up?

So whether the driver is up to date

Start the Nvidia program and, if necessary, in the device manager.

I just added a picture, maybe you know all about the temperatures

Just added a picture, maybe it will help you figure out what the peoblem is.