Dark Munich is rarely used on its own, it is a base malt (just) which means it has enough enzymes to convert itself.
It tends to make beer that is fairly dark, and sweet in this case pretty much Amber coloured.
You haven't supplied much in the way of information, like batch size, method, equipment... If we make a couple of assumptions like you are doing an all in no sparge BIAB to make a 23L batch.
I would be doing a cooler mash than usual, say 62-63oC and probably for 90 minutes rather than the 60 most people do (attempt to get more fermentable wort).
After you separate the grain from the sweet wort, and bring the wort to a boil (let it boil until it stops foaming and settles down) if you added your 100g of Hallertau (given that the AA% is around 4%) and boiled for an hour your bitterness would be around 35 IBU probably not too far off what you want for a very full bodied Lager.
I hope you meant you were adding hops to the boil, not the mash. Very different outcomes if you did.
Be a good idea to run through a bit more on what you have in mind, Info is king!
Mark