New 4K tv but worse PS4 picture?

I recently bought the Samsung UE40NU7199 tv.

I'm happy with movies and watching Netflix. Even in 4k no problem at all.

If I then switch on my PS4 (not a pro) and e.g. I think the picture is worse than on my old full hd tv. You can also see it in the user interface (see pictures).

The tv has a game mode which it automatically switches to when I turn on the PS4.

How can I fix that with the worse picture while playing?

The regular PS4 does not support UHD / 4K in games, at most when playing pictures or videos. Accordingly, the picture from the PlayStation has to be upscaled to the resolution of the television, which, depending on the television's upscaling method, looks sometimes more and sometimes less good…

So it is normal that the 1080p content seems worse on 4k TVs than on Full HD?

1080p is Full HD, so each calculated pixel can be output exactly on a physically available pixel on the television. (1080p = FullHD). UHD, on the other hand, has 4x as many pixels as Full HD, so a 1080p image has to be upscaled. There are various methods and algorithms for this, some of which recalculate and upscale the image several times. In the gaming modes of today's televisions, however, these processes are mostly switched off, since the post-processing of the input signal takes time, and you would perceive this as a delay when playing. The simplest variant of upscaling from Full HD to UHD simply combines 4 pixels of the television and assigns them one pixel of the input signal. As a result, you basically have the same picture as on a Full HD television, but UHD televisions are usually much larger than conventional Full HD televisions, which is why the formation of the stairs is clearly visible. Which method is used depends on the television, its setting options and the included gaming mode