The main reason why your toppings are burning is because your pizza stone isn't hot enough. This may seem counter intuitive but if the stone is hotter then the base will cook faster which means the overall time in the oven is less and that stops the toppings from burning.
With that in mind what can you do to make sure your pizzas are cooked throughout and the toppings aren't burnt.
Below we'll look at all the possible reasons and give you some advise to resolve each one.
This is the most likely reason and as mentioned, the problem is that the stone isn't hot enough to cook the base before all the toppings burn. I'd recommend getting a laser thermometer like this one so that you can check the temperature of the oven base before launching your first pizza.
You should be aiming for 500 °F which is 260 °C on the oven floor as this will allow for a nice crispy base on the pizza with the toppings perfectly cooked.
If you're using a standard oven to cook your pizza then I'd highly recommend a pizza stone or pizza steel that can be preheated to give you the best chance at delicious pizza.
To test this I made my standard 10 inch thin crust pizza and turned on my indoor pizza oven, I gave it a few minutes to heat up the top element but not long enough for the stone to get up to temperature and then put the pizza in.
As you can see from the pictures below. The top is starting to burn with the cheese going black and the crust around the edge already hard whilst the base was only just starting to get some colour on it.
If you're cooking in a normal oven and you have the broiler on and the pizza on the top shelf then the direct heat from the broiler could be what's burning your toppings. Try either reducing the temperature setting on the broiler or move the pizza to a lower shelf in the oven.
It's all about getting a balance between heat from the stone and the ambient heat around the pizza. You don't want the base much hotter than the outside or you'll burn the bottom of the pizza and equally if the outside is much hotter than the base you'll burn the cheese and toppings before cooking the base.
If you're finding that certain toppings are burning whilst others are fine then it could be as simple as those toppings not needing as long in the oven. In those circumstances your best option is to leave them off at first and add them part way through the cooking process.