How to keep a straight line

Can you please help me with my problems.

I’m trying to build a lawnmower controlled by two skid wheels.

The first problem is that I can’t keep a straight ahead . Although I direct the machine to the WP it turns (right or left) instead of going straight.

Second problem: I need to set ESC to Brushed With Relay mode
because in Normal mode the wheels do not rotate. I use ESCON 50/5
Servo Controller with DC motor, controller is ok. I just need to get the right PWM signal from Pixhawk 2.4.8

Can someone please check the configuration file in the attachment.

LawnMower_no_direction.param (13.4 KB)

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