When heating up a pizza, edges burn while middle still liquid (Please excuse the fact that I don't make my own pizza...)

I have a thawed (originally frozen-bought) pizza of about 25.5cm diameter, a microwave, and a convection toaster-oven, whose internal space' dimensions are  38cm x 30cm x 23cm  WxDxH. The pizza is neither super-thick nor super-thin.

When I heat my pizza in the convection oven, I can't get the different parts of it to be done simultaneously: Either the surrounding crust has its brown color slightly deepening, so it's a bit toastier than originally but not totally dry - but then the middle is still barely warm and very much liquid-laden; or the surrounding crust has blackened, charred, and is inedible, while the middle is just about properly done.

You might be wondering what temperature I'm using. Well, it's 180 degrees celsius or so, but actually I have no idea what to set it to. I was wondering perhaps playing with this setting would help, but I don't even know whether to increase or decrease it.
The key here is that you said you’ve thawed the pizza. Frozen pizzas are designed to be baked from frozen. The instructions on the box should reflect this.