Imporve model quality - grpah interpretation and further steps

Hello , I want to ask for some help.
At the moment I am trying to train my gpt-3.5-turbo-0613 chat model.

I am getting the following result

According to graph , I have a lot of doubts
Firstly , I am not sure about validation error and if it is relevant?
Secondly, I am not sure if my model is overfitted and low level of convergence.

Would you mind providing me any suggestions of how I can imporve the performance of my model , as far as I can see I have absoluetly no impact on hyperparameters like learning rate and batch size?

Can you help to interpret graph and some further steps which I can take?