Bonsai not going well - need help identification

[Just]

Hello,

I got my bonsai as a gift and I am not sure what I am not doing correctly. I would like to identify it so I can take better care of it. I cannot find what type it is.

Here are images of when I got it and now:

 

[Orion_metalhead]

1. What are your watering habits?
2. Does the container have drainage holes?
3. What kind of sunlight is it getting?
4. How long have you had it?

Cant tell what species. Looks to be some kind of variegated variety of something.

My first guess is root rot from over watering.

 

[Carol 83]

I think it is a Serissa. It actually didn't look too great when you received it. I agree with @Orion_metalhead about it being a watering problem. Serissa aren't the easiest plant to grow for many. Taking another look at the leaves it almost looks they had seen a frost. Was it outside?

 

[Just]

It was not outside but I think I kept it too close to the window where it can get quite cold at night but it gets a lot of sunlight. I got it in September and I tried to water it when the dirt is starting to get dry (I poke a small wooden stick from the draining holes and check if it got dirty).

Is there a way I could check if the roots are rotten?

 

[Shibui]

How long have you had this tree?
Serissa are one of the species that just don't like change and they are known for dropping leaves in the weeks after you take it home. Good news is that they generally grow new leaves in a few weeks as they adjust to the new conditions.
The only way to check on roots is lift the tree out of the pot. If it is well established the whole root ball will come out intact with roots holding it together but sometimes all the soil falls off. If that happens just repot with fresh bonsai soil.