Can you get better at singing with practice?

If you're using the proper techniques definitely. If you have not been taught/are not doing any research, it will be difficult and you will almost certainly develop bad habits which are very difficult to remove. If you want to improve, I advise to get a teacher, or risk teaching yourself from the internet. The technical problem with the latter is that you don't have someone who can check if you're doing it right unless you go and see someone somehow. If you are driven, progress will be made, especially with a teacher to guide you.