You can always open a dispute by pressing cmd+o that will get you to the arbitrator.
But in a way, there is nothing wrong with the trade, so you can’t really blame the other trader yet. You agreed to the max trade period.
The problem is in the Bitcoin network being maxed out with transactions right now and Bisq can’t do much in such scenarios, since it does everything over Bitcoin. Using different cryptos as base currency in these scenarios when Bitcoin is in trouble is probably the best you could do.
You can always open a dispute and tell the arbitrator that you don’t want to go with the trade that you agreed to. You will be punished by taking away your security deposit in such case.