Welcome aboard!
As you get into group riding remember the golden rule. Ride your own pace no matter how fast the group is going. Do not push it. Any group from here will wait for you at the next turn, and truly does not care if they have to wait. In fact it will make them happy that you are riding your own pace.
Any group that won't wait, or tells you to speed up is a crap group and you should leave it immediately.