Execution of failed & sync errors

I have searched the forum but was not necessarily able to find a useful fix for the “Execution of failed error & sync” issues even though I tried all offered remedies. 

Could anyone know a stable answer for the following errors? If yes, it’d be highly appreciated!

Thanks in advance.

Cihan

Edit:
The client also and constantly gives the error in the last screen shot and it is not “temporary!” All settings are smoothly set.