The horizontal cracks in your second photo just look like render that's detached and shrunk. It may look OK on the outside, but it's probably just hanging in the air. Which is good news, as it means there's probably no structural issue beneath. But also bad news as it means the render is no longer part of the building. If the render's cracked and the building hasn't then this can only occur if the two aren't attached, probably over a large area.
You should start by chiselling the render off along the cracks. You'll find out for yourself how attached the surroundings are once you start. If it's prone to all coming off then do exactly that - take it all off. Don't go filling a hole if the surroundings are hanging in the air, you'll be wasting your time, it will crack again and look worse than if you'd done nothing. Plus you'll now have a patch of well stuck new render you'll need to get off before doing it all again properly.
A hammer and chisel will tell you a lot more than an internet forum!
You should start by chiselling the render off along the cracks. You'll find out for yourself how attached the surroundings are once you start. If it's prone to all coming off then do exactly that - take it all off. Don't go filling a hole if the surroundings are hanging in the air, you'll be wasting your time, it will crack again and look worse than if you'd done nothing. Plus you'll now have a patch of well stuck new render you'll need to get off before doing it all again properly.
A hammer and chisel will tell you a lot more than an internet forum!
