How many rakats is Tahajjud?

There is no single fixed number. The beginner-safe answer is to pray two rakats at a time and keep it manageable.

Do I pray Witr before or after Tahajjud?

If you expect to wake up, many people leave Witr until after Tahajjud so it is the last prayer of the night. Otherwise, pray Witr after Isha.

No. It can be prayed throughout the year. Ramadan simply brings more people to night prayer because of Tarawih and the habits of the month.

Tahajjud is voluntary night prayer after sleep and before Fajr. There is no single fixed maximum.

It is not the same as the five daily prayers, and it is separate from Witr.

The common sunnah form is two rakats at a time. You stop when dawn is close, then pray Witr according to your school and local teaching.

Traditionally, yes, sleep first is part of the word Tahajjud. In practice, most people use it to mean the later-night voluntary prayer before Fajr.

If you plan to pray Tahajjud, you can leave Witr until the end of the night so it is your last prayer. If not, pray Witr after Isha as usual.

How many rakats is Tahajjud?: There is no single fixed number. The beginner-safe answer is to pray two rakats at a time and keep it manageable.
Do I have to sleep first?: Strictly speaking, sleeping first is part of the classic meaning of Tahajjud. In everyday use, many people use the word for later-night prayer before Fajr.
Do I pray Witr before or after Tahajjud?: If you expect to wake up, many people leave Witr until after Tahajjud so it is the last prayer of the night. Otherwise, pray Witr after Isha.
Is Tahajjud only for Ramadan?: No. It can be prayed throughout the year. Ramadan simply brings more people to night prayer because of Tarawih and the habits of the month.

“The Prophet (ﷺ) was asked about the night prayer and said: 'Two by two, and if any of you fears dawn then let him pray one raka'ah…'”

— Sunan Ibn Majah 1320 Read on Quran / Sunnah

“And from [part of] the night, pray with it as additional [worship] for you.”