I'm level 22 and I bred 11 level flower/tree poison/earth and got 2 lava, 4 flover, 4 tree, 3 mud, 4 poison. Where is my Sakura? How is it I haven't got a single one? I remember why I stoped playing for almost 6 months, a while back I bred every recomended combination for rainbow ans sun and moon and got everything but... Though others got 4-5 breeding The same. Please advice me what is it that Im doing wrong?
If you don't have a Sakura, then it is nowhere as no such thing as your Sakura even exists.
You haven't gotten a single one likely due to poor luck. You were unclear how many of which of those 2 combinations you tried, but as I said, Flower/Tree seems the more successful. Dragonvale breeding is random. Even with a 99% chance of success, it is possible however unlikely to fail 1 million times and you are not guaranteed of anything.
Rainbow and Sun/Moon have much lower chances (something like 3% maybe as per the other question) so your tale is not uncommon. It's still random so others getting more of them through better luck means nothing to your situation.
There's not really much advice to give on what you are doing wrong as there's nothing wrong being done. The only advice to give when trying to beat a pseudo-random number generator is to keep trying. It's unclear whether the epic breeding island will help, but it might be worth a shot to increase your chances. You could try other combinations though and the ones listed on the database include some information about your chances, but most of the combinations other than Flower/Tree lack enough data to be reliable so try at your own peril.
Before my generic answer about your odds of success, I do want to point out something very important about Sakura. Tree + Flower is the only combination! The tricky devils at Backflip originally allowed any combination of Fire, Earth, and Plant, but that was changed in late 2012. If you are breeding with another combination, unfortunately, you are wasting you time.
As skovacs1 pointed out, there is no guarantee of breeding any dragon, so bad luck can always be involved. It is a common misconception, called the Gambler's Fallacy, that after doing something involving chance X number of times that your odds will be better on attempt X + 1. That is not actually the case. If you've failed X times, those attempts are over and the results are known. Your future chances get no better (or worse), so if you've had a 10% chance the whole time, then each attempt has a 10% chance no matter how many attempts you make.
Using the Breeding Sandbox combo finder, we see their prediction is a 10% chance, with an average fail time of 7.94 hours. That means, if you have average luck, and you started now, and you were available to cycle dragons and start new breeding the instant they finished, it should take around 79.4 hours to get one Sakura.
7.94 hours/attempt / 10% chance of success/attempt = 79.4 hours/success = ~ 3.3 days
Naturally, if you are using the breeding cave and the EBI you can cut that in half. Good Luck!