Guys one fundamental question - where do you actually trade?

I had a sell/trailing stop order by Kraken today in the morning and during the dip - it didn't fill !!

So I quickly made a sell/market price order - which also didn't fill !!

Then I even more quicky made a sell/fixed price order which finally worked - but very late and I could have earned much more

Do you have similar experience? Do you know which exchange actually WORKS during high load situations?

Thanks