Ramadan Karim all w kol sana wento taybeen.
Paris, the length of the taraweeh depends on:
- how many Rakaa's, some imam's pray 8, some 12, some 20! (even if they pray 20, you can do 4 or 8 or whatever and leave)
- whether the mosque and the imam you're praying behind wants to cover the entire Quran in the month or not. Some imams read short verses and don't intend to recite the whole Quran in Taraweeh over 30 days. Other imam's want to read the Quran twice in Ramadan, so once every 15 days, and those obviously pray longer per day (One Ramadan I did this and it takes around 3 hours per night or so).
- of course also how the imam recites. Some imams rush through it, others recite the quran slower.
Because of this Taraweeh could take you anywhere from 1/2 hour to 3 hours. But its sunnah, so do what you can do only.
I also believe taraweeh begins on the eve of the first day, so the night before the first day.
The first day will be either Tuesday or Wednesday.
Happy Ramadan all again.