hi there! i found these tree on my garden, im trying to know if this is a bonsai.. wich one and the age.. the size is around 40 cm.

nope; it is not a bonsai; there are lots of rule before something becomes a bonsai.

The succulent plant you have there is not a woody species and as such will not ever be a true bonsai. It is a species of jade

ok, thank you for your answer. It's possible with some work that this tree became a bonsai yes? The JAde species it's just like mine but mine its really bigger..

Yours is the crassula ovata, one of the jades. And no, it will not become a bonsai, as it is not a woody species. You may treat it as one, but it will never be one.

www.google.com/search?q=crassula+ovata