I learned alot in Barcelona and finally got to sit down for a nice plate of paella and a LARGE glass of paella on my last night. A month is the right amount of time to be gone...longer is too long. Shorter is ok, but not too short if the travel is long. Travel is a good opportunity to enjoy, but also to learn and be exposed to new things. Traveling with Saliou was an education. Traveling alone and navigating on my own opened possibilities for me in life.
I will definitely travel again, alone.
I will definitely pack much lighter. Do more homework ahead of time. Do tours of monuments/etc alone, if possible. Take the time to purchase the correct tickets. The phone worked out really well, just buying data with Airalo. Next time, be sure to purchase for all the countries at once if possible. I did Spain and France separately, which was dumb. Remember that train lines can cross each other more than once. Riding bikes is a great way to go. Cars move slowly in Paris so it's less dangerous there than here in Colorado.
Go find dinner in the immigrant communities. It's less expensive and more interesting.
Spend time on the Seine.