This isn't a racing game. By having the speed limiter off, you've eliminated the challenge. I think the delivery times are based off the truck speed limits. So in order to have a challenge, turn the speed limiter on, realistic fuel, driver fatigue, realistic air brakes, standard shifting.
You're playing a game called Euro Truck Simulator 2; the key point is where it says 'Simulator'. You may not like it, but speed limits are just part of truck driving, and since truck driving is what ETS2 is aiming to simulate, then it should come as no surprise that there are speed limits. In most of Europe, the speed limit for trucks is 90 km
Turn off "traffic offenses" in the gameplay option and you never get a fine anymore. If you mean the "Truck Speed limiter" governing the truck to max 90 km/h, you can turn that off too in the gameplay options. However the External Market/Contracts are always speed limited so if you want to go faster, don't do external jobs.Simplest answer, UK doesn't use metric on roads, so your GPS will give you goofy speed limits. If you convert your settings to mph you will see round numbers like 30 and 60. If you use a conversion chart then no it's not an exact match so they round it off to the nearest whole number, both in game and in real life.