website got messed up, plugin issues after installing my theme?

On my wp network I created a new site,
first all looked good,
later today, the website got messy
even after disinstalling my theme, i cant get my website running in the default wp theme
plugin issues?
I dont know if i just can turn off all wpmudev plugins, since they are also needed on my other site in the network.
How can I have a site up again?