Moderate Layover in Frankfurt Airport

Lounge is a great idea.

If you want to get outside for a walk, the area around the terminals are not really "fresh air". Constant bus and auto traffic, no green spaces that I am aware of. You could take the metro to Gateway Gardens, first stop from the airport towards Frankfurt. It has a large park adjcent to the metro stop.

Alternatively, you could exit the airport and walk about 10 minutes to the Squaire. This is a a large building with the DB train tracks on the lower level with multiple shops, restaurants, hotels, and offices above. It is connected to Terminal 1 and the walk is all indoors. One or more of the restaurants may have outdoor seating in the summner...I don't know.

I think you have the right idea with the lounge, but there are some places to get fresh air/sunlight like this: https://www.frankfurt-airport.com/en/airport-guide/sights-and-events/visitors-terrace.html

I don’t think 5 hours is too short to leave the airport. You could leave the airport for an hour walk in the city and be back in less than 2 hours.

I was in FRA over Christmas and noticed they had some sleepingh cabins for rent. I am not going to say they were cheap, but if I were you I would do 3 hours and maybe arrive in Poland a little fresher. Many years ago, when i had pass to several lounges, I remember that one in FRA had a shower, that was nice, but I dont remember which one and wouldnt know how to buy your way in today.

We had 3 hours in FRA last month. We just walked around and spent time in the different shops-- I have access to the Lufthansa Lounge and it was fine. They may have a requirement that your flight must be leaving within 3 hours to prevent too many people hanging out. There are a number of Lufthansa Lounges to choose from.

If I had more time, I would've taken the shuttle to the B gates where there seemed to be more things to do. We were stuck in the A, Z gate areas. There are many places where there is passport control, I don't know once if you are in a secured area if you could leave. I know once we were in the Z gate area, there was no going back as far as I could tell.

The airport struck me as a very utilitarian place to get people from point A to B with the de riguer duty free shops and some German fast food type eateries. I was in Schiphol and Incheon recently and those airports seemed to be designed to give travelers fun things to do and places to hang out while on a layover. I didn't get that vibe in Frankfurt.

With 5 hours, head over to the Squaire/long distance train station. Lots of restaurants and you can go out side and view the Taunus Mountains and the Frankfurt City Forest which comes right up to the airport. The air is better over here. Have lunch at Paulaner. It connects easily from A & Z gates. Which airline are you using? Google your flights to see which terminal you arrive and depart from. If anything is at Terminal 2, you will need to add some time onto getting there from Terminal one, or vice verse.