It takes time to get faster. I have improved my speed considerably over the last several years due to many factors including riding more, getting a better fitting lighter bike, and riding lots of hills, and riding with people better than me. What I found, is that by trying to ride with people faster than me, even if I can't keep up the whole ride, is a great interval training exercise. For example, we have a very large club, so the pack breaks into many smaller groups. I'll try going out with the fast group, hang on as long as I can for dear life, get dropped, recover, then jump on the back of the next fastest group when they pass, etc. Or sometimes, I'll go out a bit before everyone to warm up, and again, jump on the back of the fastest group, see how long I can sit in, move to the next group, etc. What I have found over time is that I can stay with faster groups for longer periods of time. I also learned a lot of bike handling skills by riding with better people, just imitating their style, when they climb out of the saddle, etc. Learning better gear management for optimum speed. Like, I used to shift down as I'd crest a steep hill, now I just jump out of my saddle. Riding very hilly and windy courses are another way to crank up the intensity.