Level doesnt open in Unreal 4.12.5 without errors

Hey guys,

I was working on a Project lately and a specific Level within that Project. Everything was working until I closed the Project and took a break. When I came back to start up the Project everything is still fine. I went on to open the Level but nothing happens. Double-click it, nothing happens. Open the “File”-“Open Level” tab and select the Level and open it, nothing happens. When I left click it it says “Failed to load Assets”, I open the message log to look for Errors, no Errors at all anywhere. I have no idea what to do as this Problem seems pretty unique and uncommon. I would appreciate any help.

Assets I was working with:
-InfinityBlade:Grass Land all Assets
-Starter Content
-Foliage Starter Kit by fighter5347

Edit: For some reasons sometimes it shows “Failed to open Map file […] Something with older/newer Version” resulting in a screenfreeze