Looking for recommendations to travel through the black Forrest or on my way to Mannheim from Italy. Travelling by train or bus but prefer train
Your obvious place to visit is Switzerland and the Black Forest.
For Switzerland, I recommend a few days in Interlaken. Then you could stop at Lake Constance (The Bodensee) for a day, then proceed to places like Triberg, Friberg, Titisee and Baden-Baden.
Where in Italy and how much time do you have?
You should tell us where in Italy you are coming from and how many travel ays from the the time you leave Italy and when you want to be in Mannheim. I see from other posts you will be around Lake Como, but where exactly?
Starting from Milan, you have three main rail routes to build an itinerary from:
1. Milan - Stresa (lake Maggiore) - Brig (close to Zermatt) - Spiez (close to Interlaken) - Basel - Mannheim
2. Milan - Como - Lugano - Luzern or Zürich - Basel - Mannheim
3. Milan - Tirano - St Moritz - Chur - Zürich - Basel - Mannheim
Route 3 is the most scenic, followed by route 2 (if you travel on the old Gotthard railway and not the new tunnel), but route 1 has good side trip potential.
If your starting point is further east, like Venice or Verona, then you can go thru Austria instead of Switzerland
Corollary to Rt 2 & Rt 3. For scenic travel through the Black Forest from Zurich, train to Singen, then IC train to Mannheim via the Black forest railway. Takes 2 hours longer than the fast way via Basel, but through the heart of the Black Forest. Time can be shortened by 25 minutes by switching to ICE train at Offenburg at extra cost.