attiny85 bootloader

can also help me who with a boot-loader for an attiny85
I have the hex file, and I want to reverse it

https://www.google.com/search?q=arduino+decompile+hex+file

You can dissasemble the code, but unless you know how to read assembler you're still not going to really know what the code is doing. You can't get back to the original source in C++ from the hex file.