Worrying about a baby's sleep can be so overwhelming, and you can become really anxious about doing the things you know work best. Short naps are so discouraging as well. I've been there, many of us have, and it does pass but here are some thoughts as well.
At 5months your baby doesn't need a lot of special, baby focused activities. Watching people in a cafe, seeing the sky or trees from her pram, playing on a mat at home or watching you cook/tidy..talking to you and your mum, hearing you read or singing songs to her ...all those things are great for her and you don't need to feel guilty if that's what she does most days.
Although she doesnt need baby groups or classes, you do need company and support, so you also don't need to feel guilty if she has a day or two where she does get overtired or you miss a wake window. It won't harm her, in the same way that we can cope with a night or two of disrupted sleep. Some people, even as babies, just need less sleep or sleep for shorter periods. If she is generally getting some sleep and doing well overall then don't feel bad if one day you go out and she misses a nap.
Also at this age she will change pretty quickly (I know to you it won't feel quick!) my eldest for months would only nap on buggies and carriers so I had the opposite challenge of never feeling I could stay and relax at home - walking, walking, walking for hours of his life to keep him napping. But he changed eventually. We just kept trying cot naps every now and again, accepting that on many days when we tried it wouldn't work and we'd just cope with the slightly earlier bed or grumpy afternoons.
His siblings had other sleep challenges and really my main lesson from all of them was to do what you need to in each phase but keep an open mind to trying a new thing with the attitude that it might go better than you think, and if it doesn't you will all survive the short nap/early wake/late night or whatever the challenge is in each phase.
I also think the best thing you can do as a parent is trust yourself. Seek advice, but try to let go of the stuff which doesn't work. You know your child best and you know yourself so give yourself permission to try a day out of your gut tells you that you need it (and with an extension being built that's all the more reason you might) but equally give yourself permission to be home with her, if that's what feels right.
This stage is so hard, I think 3-6months was my least favourite bit of babies. You have my solidarity 💐