Serial binding OH3 delay between strings

Hi, i could not find any information about my topic, so my problem is that i am sending data over serial binding from AVR to RPI, with data sending and receiving everything works, but my problem starts when i want to send multiple strings to RPI that changes items, i have to wait aprox. 200 ms for sending next string because if send, lets say “string1” delay 50ms “string2” RPI thinks it is one string as “string1string2”. I hope someone understood what i mean.

Is there a way for RPI to understand that the string has ended? (Some special char or something like that)

Or for RPI to send some acknowledgement that it has received and processed the string? (And is able to receive the next string)

Baisicly i am looking for something that can reduce the delay… I would really appreciate if someone could help about this, thank you very much.