How to collaborate with an experienced researcher as a first year master student?

It seems to me that you are looking more for reassurance than advice. There's absolutely nothing wrong in seeking that on an online forum, but you must first speak to your professor and senior students working in the group. The internet is comfortable in anonymity, but you must not develop an aversion to asking people for help in person. That may be far more harmful than being stuck on a research project.

Now, remember you are at the very beginning of a research career. Your professor has spent years and years. Isn't it unreasonable to expect yourself to generate ideas at the same pace? To answer your question, there is certainly an inexperience component. Whether you are doing something wrong can only be ascertained by your professor. Most likely, you are worrying needlessly. There is, however, always a chance that this line may not be ideal for you- you will have a better idea of that by time your program ends. Your professor will be invaluable here too, but you need to take the first step and open up to him.