Does he like me or am I overthinking?

I dated a guy for three months and then he broke up with me. Throughout our relationship he had two best friends. One of his best friends recently started messaging me on Instagram (3 days ago) He asked to hang out the next day and so we brought our dogs to the park and talked. We texted throughout the rest of the day and at the end of the night he asked to hang out again the next day after work. He never mentions my ex boyfriend by name but I know they are still close because they recently celebrated his birthday together and even had lunch the same day we went to the park. I’m not sure if my ex boyfriend knows we are hanging out. I’m not even sure why he is starting to message me and wanting to hang out. Me and my ex boyfriend didn’t end badly and remained close friends up until recently (it’s been a few days since we talked and maybe a week since I last saw him). I don’t know if hanging out with him a second time will do any harm or lead to anything. For all I know, he won’t want to hang out after tonight. Or he may want to continue. I’ve never been in this situation so I don’t know how to handle it.