The phrasal verb 'come along' is often used in less formal contexts in English in order to ask how someone is doing or progressing.
If something or someone 'comes along', it can mean it arrives or appears. You might be expecting a train to 'come along', or waiting for an opportunity to 'come along'.
If you ask someone to 'come along', it means you want them to come with you. In this context, to 'come along' can mean 'to go somewhere with someone'. You might ask your friend to 'come along with you' to a party or to watch a movie, for example.
When you are talking about progress or improvement and you say something is 'coming along', it means to improve or develop in some way. So you can ask someone how their project is 'coming along', or you can say your English is 'coming along' since you began studying.
Some additional examples with 'come along' are:
Two friends meet at a conference. One is feeling hungry and wants to eat in a restaurant. The other asks...
"Would you mind if I came along with you to dinner?"
A woman was mugged in the street and her handbag was stolen. Luckily the police arrived just in time to help her.
"If the police didn't come along when they did, I could have been hurt very badly."