Problems with Intel Celeron N3350

Hello fellow members,

I have Manjaro KDE Plasma running on a USB. Now I have that strange issue, that on my Trekstor Primetab C13b the display is going off and on randomly. This happens as follow:
I start up from the USB (gen 3.0, 32 GB). Everything is normal first. Then after some time browsing through the internet or installing themes the screen starts going black. If I do not touch the mouse, it turns back on and I can see that the backlight or so is stuttering. Then it just goes randomly on and off, over and over again. Sometimes it goes back on, if I leave it for 10 seconds or so. Sometimes also when I move the mouse aggressively…
No clue why this happens.
Same thing with Manjaro live and installed.
On my Lenovo laptop, which also uses integrated Intel Graphics, I have no problems with this.
Could it be that Celeron N3350 HD 500 graphics are not supported by Manjaro KDE Plasma?
I chose both Free and non-Free drivers, always having this problem after a couple of minutes working in the OS.