A class is not an object. The object would contain the data, but the object is not the same, it is a new one.
think of a class liek a cookie template and the objects are the cookies. Two can be colored and flavored differently but they both would look like the same cookie. xD
If you are comming from Unity, there is no DontDestroyOnLoad like behaviour in UE4 that I know of. But you could use stream levels and do it this way.
To transport data from one level to another you could either save it to an .ini file if it are just a few variables and cheating is no problem or you could create a binary that is loaded an populates the GameState data again in the next level.
Here is a huge document on this topic and it really depends on what you wanna do serialization.
Here is also a nice discussion about this topic