So I found a Samsung charger with no quick charge just a normal one. But it outputs 5.3 V and 2 A. I've read at other forums that it shouldn't pass 5.25 V. So I wonder if it still safe to use it to my Raspberry Pi 3 B. If not recommend me what I should look for.
The tolerance range for the supply voltage on the Raspberry Pi is 5V±5%, that means min 4.75V and max 5.25V. But ±10% should still be safe for electronic devices, so 5.3V will probably work, even though it is not perfect.
I have even read someone used a power supply with 5.7V, which still seemed to work fine. What I have read as well is that the Pi has a protection circuit which will cut off the power if it exceeds 6V.
So yours is probably fine and will not cause any damage.