Some plugins deactivate repeatedly

Hi all,

I am having issue that maybe half of plugins deactivate constantly and repeatedly, every few hours or so. Have to come back and activate them again. The website is woodenhottubsale.co.uk
Funny thing is that other website badetonneholz.de which is the same but language, works well.

I am kind of lost what to do, googled for that maybe someone faced this problem previously, but did not find anything.

Your thoughts would be much appreciated!