I want to go from CDG airport terminal 1 to Eiffel tower? Please advise the best transport option so that I still can see the firework.
The Paris RER and Metro trains do run on July 14 (France national day) from CDG to Paris Eiffel Tower. The route would be RER B from CDG Terminal 1 to St-Michel Notre Dame station, transfer to RER C direction Versailles Chateau-Rive Gauche until Invalides station and walk from there.
Note that all Metro/RER stations in Paris anywhere near the Eiffel Tower on France National are incredibly busy from around 7pm till midnight. It may take 60 to 90 minutes to enter a station and board a Metro/RER train after the fireworks are finished due to the sheer number of people lining up at the stations to get home.
Car traffic is also extremely congested due to the amount of people walking in the middle of the street after the event. If you're on a tight timeline I would not suggest trying to watch the fireworks from anywhere near the Eiffel Tower, but perhaps from far away high vantage points such as Montmartre. It will still be busy, but not quite as bad as near the Eiffel Tower. Just be sure to give yourself ample time to get anywhere on the evening of July 14th in Paris.