When cloning first add "--recursive" option to clone including all submodules:
If you forget use the command below.
git clone --recursive https://github.com/Gerold55/WasteLands_Survival.git
The submodule folders will be empty if you don't.
If one of the submodule folders is empty use:
git submodule update --init
This will clone all missing submodules.
To pull all changes in the repo including changes in the submodules use:
git pull --recurse-submodules
If you develop on projects with submodules like wls I recommend configuring your git to warn you if you have changes in submodules that are not on their remote.
git config --global push.recurseSubmodules check