quand tu veux means 'whenever you want' in French.
Tu veux means 'you want' in English.
mais tu veux ... means 'but you want...' in English.
Veux-tu m'épouser ? means "do you want to marry me?".
"do you want "
"veux-tu m'épouser ?" means "do you want to marry me?" in English.
Qu'est-ce que tu veux ? means "What do you want?".
qu'est ce que tu veux manger?What do you want to eat.
Whenever you want
'je sais ce que tu veux dire' or more standard: 'je vois ce que tu veux dire'
"je veux dire" translates as "I mean / I want to say" Tu vois ce que je veux dire ? = See what I mean?
I don't quite know what you mean. 'Quand tu veux' means 'when you want', which doesn't fit with the rest of the question.
The cast of Tu veux ou tu veux pas - 1996 includes: Nils Tavernier Florence Viala