Picture of my Teamspeak overlay right now

Hello guys and already thank you for viewing this thread.
I have bought a 28" UHD (4K monitor) yesterday and everything works perfectly exept my teamspeak overlay.
Before using my 4K monitor I have used a 1920x1080 21.5" monitor, which is now my 2nd screen.
I can now only see 20 channels in the "channels window" but before I could fit around 40.
Also the letters changed their size, the menu tabs are farther away from each other and resizing everything with "Ctrl. + Mousewheel" only makes the chat correct for once.
I tried restarting my computer several times but there is no change made to the interface.

I want to use teamspeak on my smaller, old monitor to have it open when gaming.

I would appreciate any form of help, if there is anything you got to know additionaly, let me know

I already thank you very much! :)

PS: On my 4K monitor does it work perfectly, so I would like to hear, how I change on which monitor Teamspeak should be started