Tips: Hue-shifting makes the skin more decorated, but it is really hard for skin beginners to do this skill. Once you use it, you'll reach your full potential!
To make mob skins, you'll need to use PMCSkin 3D editor. It allows you to edit mob skins. I have two tips for skin editing : Use hue shifting. For example, I dont used dark orange to shade, I use dark red instead. (A little bit lighter) Overlaying clothes. It helps you make the clothes look a bit more realistic. (Can also be used to do hairstyles)
Try getting the latest version of MC, then restart, and try installing the latest Java runtime, then re-install minecraft. If it dosent work then maybe some servers are down. Try again later
Try deleting some abandoned files. Or clean up your main disk partition properly, then uninstall Minecraft Bedrock, restart your computer, and reinstall it.. That should work. Otherwise, contact Mojang for assistance.