Another quick post because I was only there for a weekend and just in Paris. Note that you should brush up on your French because English speaking is minimal.
I took the Eurostar tunnel train from London to Paris. It wasn't too expensive, if I remember correctly, and it was a quite comfortable ride. From the train stop, we Ubered to our Airbnb in the Latin Quarter. We got a simple studio with bunkbeds and it was ~$80 per night, plus cleaning fees, (divided by 2 people, so really not bad.) The location was great and only a few blocks from Notre Dame.
Here's what I did in Paris and what I recommend you do. :)
EAT HERE. I couldn't read anything on the menu so it was a shot in the dark but everything was so good, we ate there twice in two days. It's also right near Notre Dame, (and right around the corner from our place.)
See the Eiffel Tower at night.
Have a picnic or just stroll through Jardin du Luxembourg
Check out the architecture throughout the city.
Tour the Catacombs and see how the city of Paris disposed of their dead
Watch the sunset over the city from the Arc de Triomphe
Mosey through hip and trendy Montmartre
Eat all the food. Baguettes, frog legs, wine, crepes, cheese, macarons, pâté. All of it.
Obviously, there's much more to do, the Louvre being another big one, but with the short amount of time I had, the above made for a perfect weekend.