We have this gen. trying to run our food concession trailer. The trailer has a breaker box with all 20 amp breakers.I think all the wiring is 15 amp wire. I use 30 amp rv extension cords 60 to 90 feet depending on how close I can set the trailer due to the loud noisy of the gen. We have 2 steam cookers,microwave,waffle maker,coffee pots, refrigerator freezer,interior lights etc in trailer.The breaker pops on the generator if we try to have everything on. What do I need to do to prevent this.

Without knowing the breaker size, and the load of each appliance, the obvious answer is the load is too great for the breaker, so less load must be connected.

What you can look for is that the load is "balanced", which means there may be too much 120 volt load on one leg, assuming this genset is 120/240 volt, and some needs to be taken off that leg and connected to the other leg.