First of all, you should confirm that you are actually supposed to work from 07:00 to 20:00. It is quite possible that these are merely business hours, but you are only expected to work 8-9 hours within these 11 hours.
It is quite possible that teams even have overlapping shifts to cover the whole range, or that you have a certain "liberty" of starting anywhere from 7 to 9, etc.
It is also possible that you are indeed expected to work 11 hours. There exist employers like that, especially those that dub themselves as "startup". Presumably, you are entitled to some super benefits in case the startup is successful. But be sure you have in writing what you get (if you opt to take it).
Does the law allow for that? No. But who cares. Ironically, in Germany, "Recht" (law) sounds much like "gerecht" (just), and it seems like "Gerechtigkeit" (justice) comes from "Recht" (law). That's not the case.
(Actually, there is a trick so the law will indeed allow for that, and which will get you cheated over the employer's half of social insurance pay. Be sure not to work as subcontractor.)
Politicians always like to point out how we're a democratic, constitutional state where people are equal and the law applies to everybody (blah blah), but that isn't the case. In reality, it is only true when it's opportune.
Law has it that you must not work longer than 8 hours per day (and your employer may not ask for that). Except... it can be 10 hours, exceptionally, if on the average over six months it's no more than 8 hours.
The law has it that you must have 45 minutes of break if you work 9 hours or longer (30 mins otherwise), breaks may not be split up to intervals shorter than 15 minutes, you may not have more than 6 hours of work in one block, and you must have 11 hours of rest before going to work again. The latter is just about the case if you go home at 20:00 and start again at 07:00.
Law also has it that you cannot and must not work during vacation, and you cannot and must not sell vacation (not just illegal for your employer, but also for you). You cannot, except in very drastic situations, e.g. when the company would otherwise go bankrupt, be told to go on holiday, or to cancel holiday.
Law has so many other silly things (genders are equal? are you kidding me?). Nobody cares.
Reality has it that not everybody is equal, and nobody cares. Nobody cares whether it's against the law, nobody cares if you feel unhappy about it. Reality has it that not only some companies, but entire professional branches violate the law systematically, on a daily base. Reality has it that some very high profile companies will try to buy off your holidays and will force you to take holidays when it's more profitable for them. And yeah, most people do comply with it because if you don't, you'll find yourself unemployed soon enough. Not for that reason of course, they'll find another reason. Most people cannot afford the luxury of being right.
After confirming that you are indeed expected to work for 11 hours per day, your only (realistic) options are to either take it, or find a different job. If you believe that you can just say "yeah no problem" and then not work as agreed, please note that within the first six months they can just cancel your contract any time they want, without reason.
The sad truth is that you aren't going to negotiate anything. Employers who do ask such working hours know darn well what it is that they're asking, and they know darn well that it's illegal. They also know darn well that they'll find someone else to work in these conditions.
It works until it doesn't work any more. If anyone wonders why there's such a problem with seeing a physician in Germany, that's exactly the reason. Long education, high qualification, high responsibility, 11 hour work days (assuming no stand-by, which despite its name really isn't stand-by but 30 hours of work with, if you're lucky, 3 hours of sleep from 2 to 5 AM). Getting cheated on rest periods every time, and getting paid 65k gross for that. Not happy? Go shit, there's plenty of others who will do it. Until there aren't. Which is where we are now.
Wow, that comes as a total surprise.
Eventually, the "startup" kind of employers may face similar problems finding people who are stupid enough to do it anyway, but so far that's not realistic. Realistically, you can take it or leave it.
...but the working hours are supposed to be 8 am till 7 pm,...could it be that 8am to 7pm is actually meant to be office hours/when they expect employees to typically work from? Meaning, you work for 8 hours a day but they prefer those 8 hours to be anywhere between 8am and 7pm.