after rebooting my NC server keep on getting an internal server error | no clue what to do
The server encountered an internal error and was unable to complete your request.
Please contact the server administrator if this error reappears multiple times, please include the technical details below in your report.
More details can be found in the server log.
Since you are probably in the best position here in the forum to access these log files, it will neither help you nor can anyone help you if you publish this standard message here.
You will have to look in your logfiles to get more insights.
If you don’t know where to find the logfiles, you have to fill out the support template with informations about your server and setup.
The nextcloud logs are per default inside of your data-directory.