It would be nice to first adjust the frontend that you use, just pay attention to the language used, whether it is PHP, JavaScript, or Java and others. Then adjust to the backend language and select the framework that you understand from that language.
But if you want frontend and backend interactions across languages, it also doesn't matter, it's just that you must be able to adjust the situation when moving between projects frontend and backend.
For the database still use SQL, it doesn't matter as long as it's not a very large project, if indeed the data you will manage is very large then use NoSQL like MongoDB.