You don't say which cities you will be visiting. Big cities have lots of tourists as well as trade fairs so their menus may often have English translations.
About 20% of Germans are either vegetarian or vegan, so be prepared to have many lighter options to eat. If you are here during May, it is Spargel season with tons of white asparagus on every menu.
What guide books are you reading? I have never seen horse meat on a German menu.
Don't knock boiled beef until you have tried it. It is just like having pot roast.
Duck is to be found in fine dining establishments, so not sure why this is scary to you?
Regional specialties abound. In Frankfurt it is Green Sauce. Sort of like sour cream and chives on baked potatoes, but with more herbs and way tastier. Served on boiled potatoes with a hard boiled egg, or on a schnitzel (Frankfurt schnitzel), on pike fish, or on that dreaded boiled beef you are afraid of.
Be aware that sometimes menu translations can be a bit off. Meat loaf is often seen on German menus but it has nothing to do with American style meat loaf. Limonade is sprite and not Lemonade. Spare ribs are not usually barbecued ribs and will often be listed as Spear rips.
There are 100's of different kind of sausages in Germany, so perhaps you will find some you like. We have fantastic cheeses and breads, all kinds of mushrooms, delicious fresh fruits and vegetables.
Salads pretty much always come with a house dressing, they don't ask you what kind you want.
Try the Flammkuchen, a thin crispy bread that looks like a pizza but has creme fraiche and various other ingredients on it. My favorite is mango, spinach and mushroom, but others like onion and bacon or perhaps salmon.