Thanks for the tips.
But I have another question:
Now I use intuitive F2L, never learned the algs (except 2 for beginners method), is it still usefull for me to learn some F2L algs???
Don't bother with that now. Just check all the F2L algorithms to see how the cases are easily solved (most of the algorithms will just be what you do intuitively already).
anyway, just practice. Judging from your video, don't train look-ahead yet. Just solve F2L over and over until you don't have to think on how to solve pairs anymore (you have some huge breaks thinking of what to do). After some practice you'll be used to solve any case, and then you can start doing it blindfolded if you want (search for a pair, close your eyes and solve it, search for next pair) and then you can start practicing look-ahead.
Sub30 is pretty easy to get if you keep practicing, so good luck!