i5-4990 and GTX970 overheating problem

[mortyaut]

My Spec is:
Intel Core i5-4690
Nvidia Geforce GTX 970
Motherboard: ASUS H97-PRO GAMER
But
I chose a wrong case for my system: Green X-Plus Eagle Computer Case.
I think this case has a poor cooling system.
This case has two main drawbacks.
1) It just has one weak fan and it seems that the "case fan" doesn't speed up very much when the temperature increases.
2) The case has a low volume ( 480*480*210 ) for my GPU.

And when I play GTA V for 10 minutes, the max temperature degree for my CPU and GPU is going to be like this:
CPU: 79 C
GPU: 70 C

I think this temperature can be harmful to my system.
But I don't know how I can improve the cooling system with the lowest budget.

Is it enough to add more "fixed speed fans" to my current case?
Or should I change my case? Which case is a good choice? (Cheap one )

I also want to work on deep learning tasks in future so maybe I would want to train a neural network with my GPU. I know it takes one day or more for training some neural nets so maybe I need more fans for my system.

Which "case" and "fan" is a good choice here?
Thanks

 

[johnkatsina]

Anytime you're running any game with the system I'll advice u to have a mini fan put it close to the system and watch out magic

 

[mortyaut]

Anytime you're running any game with the system I'll advice u to have a mini fan put it close to the system and watch out magic

Thanks for your answer.

So you mean I don't need to change my case? And with a mini fan (outside of my pc?), I can solve the overheating problem?

Is 79 C temperature harmful to my CPU?