When I start Minecraft the loading bar under the Mojang logo suddenly stops.

When I start Minecraft(1.14-1.15.1[I just tried the versions 1.12.2, 1.13.1, 1.14.4 and 1.15.1]) the loading bar under the Mojang logo suddenly stops moving at approximately 90%. I'm having this issue since I downloaded the Wurst client for 1.12-1.12.2 (Just for single player and anarchy servers such as 2b2t)

I already tried:
-completely deleting the Wurst client
-reinstalling Java 8
-reinstalling Minecraft
-deleting 1.14.4&1.15.5 and recreate them
-googling the problem