I usually pronounce "will you" as "/wɪ/ + /lju:/", but seems that people have some troubles understanding me (at least here in the UK). Is my pronunciation wrong? That's the way we usually make the linking sound between a consonant and a vowel. If so, what should be the proper pronunciation? Should this be as "/wɪl/ + /lju:/" (that's how google translator pronounces it, apparently)? Or there's no way to connect these words and I should say "/wɪl/ + /ju:/" ?
Before being able to respond, I would need to know whether or not you are a native English speaker and which region or country you come from. There are several regional variants in English which can to some extent be mutually unintelligible; for example, I am Scottish, from Glasgow, and once knew a man from the Newcastle area whose Geordie accent I found very difficult to understand.
What is the pronunciation of “Will you” in fast/connected speech?
In standard American English, without a regional accent, it usually sounds like the regular word "will" (not wl, wll, wull, or well) attached to the regular word "you", so "willyou". I don't believe any sounds are dropped or omitted. Arguably, the ll sound is equally connected to both the first part and the second part of the word "willyou".
The vowel sounds are heavily dependent on dialect, though the 'i' in will is usually a short one. The vowel in you might be a schwa, a short 'a', or a long 'u' or 'oo' sound.
What makes it fast/connected is what happens to the 'l' and consonant 'y' sounds. In my experience, it ends up like the 'lli' in million, which is, I believe, much like the ll that used to be considered a separate letter in Spanish - but only in Spanish-Spanish (e.g. Castilian), not Latin American Spanish.