@SAWY_Learning welcome to the community.
what I am doing for theme I will just explain to you
first go to lms.yml file
COMPREHENSIVE_THEME_DIRS:
'/edx/app/edxapp/edx-platform/themes' hear my theme folder in this disc
enable COMPREHENSIVE_THEME: true set this to true
default side theme:' my theme name'
make lms -restart
then go to studio.yml and same apply as above and hit make studio-restart
then go to lms shell make lms-shell paver update_assets --settings=devstack_docker
then comes outside the shell of lms and hit make lms-restart and the same follows as studio
your theme changes will appear u can use this command to show logs of lms if any issues face make lms-logs
if requirements relate issues hit