Hi @immanuel113
welcome to the arduino-forum.
How did your write your code?
Did you add new functions step by step
testing each added function right straight-forward after adding one single function?
or
Did you write it almost at once and then started testing?
Well if you wrote it all at once you many lines of code that can have a bug.
Can have not must have.
The more lines of code the more time it may takes to find the bug / the multiple bugs
Sounds like your ESP8266 resets again and again.
You are working on an informatik project and what is most needed in an informatic project is - guess what ? information
From having posted your code, telling it is an ESP8266, an OLED display an nrf2401 and blynk there are minimum ten-thousands of possible reasons what might be wrong.
Nobody will write 20000 pages tutorial for you to cover all possible reasons
and you don't want to read them.
So speeding up soling your problems by a factor of 1000 times faster is to provide more detail-information.
What detail-information this is
is explained in this tutorial
You should also add the serial output that shows what your ESP8266 is doing.
It is printing important information to the serial monitor
post the serial printing as a so called code-section.