Fat experiences

I'm actively gaining and I reached a weight of 135kg in 2 years, from a starting weight of 85kg.
But in the past months I got stuck at this weight without gaining.
I've been less active so my guesses are that I'm losing muscle and having fat simultaneously.
Does someone know how to continue to gain?

Unfortunately,getting stuck in your weight gain progress is something that will happened to every gainer eventually. One of my worst plateaus was when I reached 300 pounds and did not gain a single pound for almost 6 months. It was very frustrating to go through because I was consistently overeating and began drinking very calorie dense protein shakes after working out.

All I can really say is keep doing what your doing and be patient with your body

This is actually the perfect time to prep your body for the next round of weight gain. And the best way to do that is being more active. Go for walks. Use a resistance band. Do some kind of light to moderate exercise. If you keep up with your calories, you will not lose weight, so don't worry about that.

It's possible to shock your body into gaining by dramatically increasing your daily caloric intake above the norm and sustaining it for a few weeks. I challenged myself to a minimum 6,000 calorie daily diet for forty days, occasionally reaching 8 or 9k, and packed on 33 pounds. It was hard on my body, though. It was physically challenging to eat enough every day to hit that target, and I was consuming so much sugar it disrupted my ability to sleep.
I don't recommend it if you have health issues, but it is one way to get results.

I don't recommend this even if you are healthy. Sure you can shock your body into growing more, but it's very common for the weight not to stick after that. It's also even more common for those that do this to end up needing to lose the weight later.

How you gain is more important than how much you gain. If you don't put in the work to prepare your body for the additional pounds, then you are preparing yourself to lose them.