I already wrote that when I uninstall The Checkout module, I also delete folders /modules/thecheckout, /themes/mytheme/modules/thecheckout and /themes/child-theme/modules/thecheckout. But settings of The Checkout module still remains.
That's why I am asking you where are all other folders of that module.. I can't find it in Database.. 
Problem is that there is something wrong with css and I want to do it from the beginning.