Formal:
* আমি শিখছি (ami shikhchi) - This is the most common and formal way to say "I am learning".
* আমি শিক্ষা গ্রহণ করছি (ami shikkha grahon karchhi) - This is a more formal and literary way to say "I am learning" which translates to "I am receiving education".
Informal:
* আমি শিখতেছি (ami shikhtechi) - This is a more informal and colloquial way to say "I am learning".
* আমি শেখা (ami shekha) - This is a very informal and simple way to say "I am learning" but may be considered grammatically incorrect.
You can also add what you are learning after these phrases:
* আমি ইংরেজি শিখছি (ami english shikhchi) - I am learning English.
* আমি রান্না শেখা (ami ranna shekha) - I am learning to cook.
The best way to say "I am learning" depends on the context and the person you are talking to.