If you have photos or any other content, such as music, you could look at moving them to an external sd card. The camera app may have the option to use the card as its default storage, too.
This is an obsolete model and things have moved on since it was current - devices have more storage and memory. The result is that apps tend to assume that more resources are available to them and take up more space, meaning that you can store and run fewer of them. I have a Samsung Galaxy S2 that's now so slow as to be impractical and a not much younger Samsung tablet that is restricted in what I can do with it. On that, I've found that regularly clearing recent apps makes it a bit more usable.
According to the last-published spec for the 310, it was running Android 4.2, which I think was late Jellybean (do you have that, or can you update to it?). As far as I'm aware, that did allow compatible apps to be moved to an sd card. You have to open each one in settings and see whether the option is listed.
As Bandofbrothers1 says, 4gb is precious little space (my S2 has 16 and my tablet 8 and they still struggle).
