How do I correctly remove my custom shipping method? See screenshot: http://prntscr.com/l15jin
I added a shipping method but it's only partly working, now I want to remove it's code and all functionality from Magento. If I only remove the custom code, the Magento shop crashes.
The code is here: http://prntscr.com/l15kld
Do I need to disable or remove other things?
After removing module if site crash then it happen if module contain catalog or customer attribute and that contain source model
So go to your module and find setup schema and upgrade schema
and check which attribute created, so you need to find attribute and need to remove from eav_attribute.
Let's example attribute name is custom_attribute then
query will be
delete from eav_attribute where attribute_code='custom_attribute '
after delete done, do reindex and cache flush.
If works then mark as solution.
Looking at the first screenshot you have shared with us - if you select NO from the first option like Enabled - does your shipping method is not disabled ?
for the second point - yes as suggested by @Sunil Patel - you need to remove its attribute and other values from the database.
Actually what happened when you installed any new extension on magento - in that extension they do have Setup Scripts (Like InstallSchema, UpgradeSchema etc) - so using that script extension will generates the new tables and also a new columns on existing tables as well.
So you can also try by disabling this extension like - run the command php bin/magento module:disable MagePlaza_ExtensionName
then run rest of the commands like setup:di:compile then setup:static-content:deploy -f and cache clean and cache flush command.
It will works for you.
Hope it helps!