I have installed Magento 2 on Ubuntu server because I tried to run it on my localhost but it was extremely slow. So I installed it via Putty and now everything is working fast. My question is, where do u find the source code if u want to make some custom changes inside of the code??
Without more details here is a link that will help you find a lot of file locations: https://devdocs.magento.com/guides/v2.3/frontend-dev-guide/bk-frontend-dev-guide.html There is a section for theme, layouts, and templates. Because Magento is open source you can also look at the github for more information. https://github.com/magento/magento2
Please let me know if you have more a server question and are trying to find the files on your server.