Security of apps built on Telegram api?

I am using a telegram api based app named “TurboTel Pro”. I am happy with its different look and settings but I am concerned about the data it would take of me.

Can someone tell me what data does these api based apps take? I read in FAQ of “iMe” (a telegram api based app) that they don’t collect or they are not able to collect or see data from telegram servers but they also connect to third party servers to run some of their services.

Are they saying right? How much can I believe in them? What about third party service providers used in app? Is my data safe from third parties?

I also read that after verson 5.0 of telegram bots, api based app developers can connect their app to other servers also. Am I gonna loose some of my data in hands of other new-non-trusted companies?