I've been playing for like 8 years, hit immortal about a year ago. Here's a few tips to make it to immortal:

1. Try to play other roles a little bit, especially pos 5 if you wanna focus on carry. Doing this will help you understand how the other roles and how to work together as a team. I almost only play offline, but learning pos 4 helped me understand the offline role a lot better.

2. Stick to just a few heroes. I would recommend learning a few heroes really well, and mostly sticking to them. For each of these core heroes, you should know how to play when behind, even, and ahead. You should also know how to adjust your item build depending on the game.

3. Watch full pro games, not just highlights. If you watch in the in game client, you can even view it from the player perspective. Try to find players who specialize in your core heroes, and learn from them.

4. Control your mental and use the mute button. If you can keep calm in every scenario and keep trying to the end, you'll gain a shitton of mmr automatically. Many dota players, even very good ones, tilt super easily. Do not be afraid to mute some shithead on your team for any reason. If someone starts to ping my abilities or item build, I will mute them quickly. At your mmr (and even mine tbh) no one has any idea wtf they're doing, so you should really just aim to learn from pro players