he wanted to say "you too!" gramatically correct version should be "sen de abicim"

rica ederim :)

You = awesome. Me = grateful Endless gratitude. Thank you.

You = awesome. Me = grateful Yesss! Perfect, you got it! This is what I meant! & this is the meaning I was looking for ! Endless gratitude. Thank you so much !

I think you are asking why he is told you ''abicim'' instead of the meaning of ''abicim'' abi- ağabey means older brother as you might know. If the person you have talked is older than you , if he is your ''abi'' , it means he is showing affection as an older brother to you with saying abicim. It may sound weird but as an example son: Good night mummy Mom: Good night to you to my mummy :D It is just means showing affection as a mother :) ( I know it is weird)