How can i connect 4 stepper motors and 3 sensors to an Anduino?
Take a look at the Ramps V1.6, it is what I use. It plugs onto the AT Mega board.

https://reprap.org/wiki/RAMPS_1.6

The 1.6 has a few improvements. I like the solder in power connectors rather than the plug in ones. More reliable.

Because I already had the AT Mega board I decided to try the ramps. There are better boards now, with 32 bit processors. But as a starting point the Ramps combo is the simplest to get going and it does the job. 

Other boards may work out a little better, but the firmware is a bigger issue. Still in development.