I was talking to my friend about how to use Photoshop so I told her I tried to use it but it was hard. But then I realized that if I use it was hard then does it mean that it's no longer hard for me anymore? (in fact, I still don't understand how to use it properly) or could it be an affirmative sentence to show that this happened in the past?
"I tried to use it but it was hard" would be expected in this situation. This sentence almost sounds like "I tried and I gave up because it was hard". A listener would not assume that you tried, it was hard, but now it is not hard for you. You could also say "I'm trying to use it, but it is hard". Either way, the tense (present, future) has to match.
And yes, Photoshop is hard. But keep trying, it's a powerful program that is very useful!
To my ears, "I tried to use it but it was hard" says that you gave up on the idea of using Photoshop. You tried it. It was hard. So you moved on. It was hard. You don't care what it is now.
On the other hand, "I tried to use it but it's hard" suggests that you still want to do it. Maybe you tried many times and will try again. Maybe you still think about it sometimes and try to figure out why it didn't work. You know it is still hard because you are still hoping to succeed.