So, you can use one or the other depending on the situation. Example: “I go to the bar sometimes”. Usually when you use “sometimes”, it It used in a context of describing a regular or recurring habit. That you continue to do in the past and in the present. With “sometime” really the only way I use it is when I talk about meeting up with someone in the near future, example “hey, we should grab a drink sometime” it’s used when hinting towards doing something specifically one time in the future. Hope this helps!