New Player Here, how am I supposed to Deal with Anti-Mage?

To start off, I have high level competitive experience in Overwatch, and I am learning Dota 2 because my brother really enjoys it. I've gravitated to playing mostly POS 3 because they ususally consist of tank characters, which is what I enjoy the most. But, I've never once played against anti mage as all 5 positions and not immediately folded to him. It feels like he not only has everything, but he can also take away player agency with his mana stealing, and I just can't seem to shut him down. What am I supposed to do as an overall gameplan against him, especially in 1v1s and team fights?