Unity Editor not working after project creation/selection

I have Unity 5.6 installed, but since yesterday it won’t open project anymore.
I can select a project or create a new one, but the project won’t open.
I’ve tried uninstalling and installing it again but nothing happens.
In Task Manager I have Unity and Unity helper instances but they are doing nothing.
Please help me!

Which kind of support is if nobody cares about ?

I had the same problem.
Sometimes it worked for me to kill unity and delete all folders in a unity project except Assets and ProjectSettings.
After that i rebootet my pc and was able to open the project again.

But the real problem seemed to be the editor log file. It can be found like mentioned in How can I find editor log file? - Questions & Answers - Unity Discussions

I killed any unity instances and deleted every log files for the unity version in question. After that i was able to open a project again that failed previously.