An audio interface is a piece of electronics that makes it possible to connect sound, i.e. a microphone (singing/speech/instrument), an electric guitar or a keyboard to a computer and record it directly in an audio software (NLE).
If you want to listen to good quality audio with professional headphones and feel that you are not satisfied with the quality directly at the headphone output of the PC, you need a sound card with better amplifiers or a headphone amplifier.
My recommendation goes to Fiio, for example with the Olympus2 headphone amplifier/DAC.

FiiO Olympus2 E10K (USB-DAC)

What do you mean yes/no?

So I need it for film and music on the one hand and for video editing on the other, but only rarely, especially for standard use. I don't know for an interface about 80-200 fr. But eig. not more than for the headphones xd

It depends on what you need and how much money you want to spend.

Actually, you need more of a sound card? An audio interface is only necessary if you want to connect a professional microphone. Asus U7 external sound card is top. I have both sound cards and audio interfaces on my desk.