MPU6050 acting very weird....

Hello, today I'm messing a lot with MPU6050 breakout board GY-521. Yesterday it worked very well (I've tested it with an Arduino Uno), but today, when I've soldered it on a board with arduino nano, It kinda doens't work.. I have it connected the same as i had with the uno: VCC -- +5 GND -- GND SCL -- A5 SDA -- A4 AD0 -- +5 INT -- D2 I don't even know how to describe it, but it doesn't work with the nano. So, I've desoldered its VCC and GND from ARDUINO and soldered on some jumper wires. I've connected the jumper wires to arduino uno and.... No luck. It didn't work... I have tried to put pullup resistors to i2c lines but it didn't work either. After around 2-3h of tinkering with it, it showed some life.. When i connect the other board with the nano and the gyroscope to a battery (but gyroscope isn't getting power from the nano or the battery and it only has i2c connected to nano). It starts to work, but it works for around a second and freezes, if i plug out the battery and plug it in again, it again starts to work and then freezes in a second.. I have tried I2C scanners, IMU_zero sketches and it doesn't find the GY-521. I'm runnning a simulation of a plane with that gyroscope and yesterday it worked fine, but today it only works for a second when i plug in and out the battery.(for simulating i used this: https://www.instructables.com/id/MPU6050-Arduino-6-Axis-Accelerometer-Gyro-GY-521-B/); I would like to get an answer as quick as possible, because i'm kinda in a hurry and I don't live in a country where i can get another gyroscope in less than 1-2 months.

Installation and troubleshooting:For problems with Arduino itself, NOT your project