First time PCB layout recommendations
Normally I love a challenge, and I hate naysayers, but I'm going to recommend surrender. Consider some analogies:

"I've never driven a car before, but my boss wants to enter me into a Formula 1 race tomorrow. What tips do you have for driving?"

"I've never played chess before, but I have played snakes and ladders. My boss wants me to play against Deep Blue tomorrow. What tips do you have?"

The design of this PCB sounds pretty complex. I have been designing PCBs for more than 15 years. A moderately complex 4-layer board about 50mm x 50mm with no high speed components still takes me about a week to lay out to my satisfaction. This is partly because of the tight packing requirements, but mostly because it really does take time to get things right.

If someone asked me to lay out the board you describe, I would have to have a stiff drink and sit down. I might well turn down the job.

If this board contains no high speed digital or sensitive analogue components, then you might just get away with it. It will simply be a matter of throwing a lot of time at the problem. If the board contains high speed transmission lines between the FPGA and other components, then you will need to learn how to lay these out properly. You will also need to pay careful attention to the power distribution, especially around the FPGA.

Remember that at high speeds, the PCB is actually a component. What you are designing is not a bunch of wires, but a complex nest of inductors and capacitors.