I am flying United in Polaris (Business) class from the U.S. to Frankfurt (arrives Terminal 1), then on a separate ticket, going Frankfurt to Dresden on Lufthansa in coach (leaves out of Terminal 1). Not even sure if I will need to collect my luggage here or if they will check it all the way thru if I show them my 2 boarding passes at check in at LAX to FRA.
There is almost 5 hours in between flights. Which lounge can I spend my time? I'm not familiar with the Frankfurt airport and it's lounges (assuming all will be open in Sept. 2021)
-Is there a United Polaris or Business Class lounge in the Arrivals area that I can spend most of my time in before heading to the Lufthansa inter-Germany flight?
-Or should I go straight towards the inter-Germany flight, but how can I get into Lufthansa lounges with a coach class ticket? Can I buy a day pass? (Lounge Buddy, or on-site?)
-I hold a United Mileage Plus Chase Credit Card, a Gold American Express Delta Credit Card and a Platinum (but not super status) American Airlines MasterCard.
-I flirted with the idea of just paying the extra $350 plus to buy my oneway ticket Frankfurt to Dresden in Business Class to be able to get into the lounge to spend the layover, but is there a better and more cost efficient way?
-Heard about a Frankfurt Lufthansa "Welcome" Lounge, but is that only for Business and First Class passengers?

Any suggestions/help appreciated. Thank you!!!