[Galaxy A3, A5, A7, A8, A9 Q&A, Help & Troubleshoot] InfernoWolf19:
Before starting, please be aware that rooting will void your warranty and if the steps I have given below are not done properly, you will brick your device. Please don't blame me if you got your device bricked. :fingers-crossed::)

1. Firstly, you need a windows pc and then go to this link and download the whole folder with the name "Samsung Galaxy A5 2015 Root Method". Do not miss a file and extract all the files from the zip into the folder with a name "Samsung Galaxy A5 2015 Root Method" . Link: https://drive.google.com/drive/folders/1Yx3NgLaEfxW-vYdoKSk0u3N3KbEbktlP?usp=sharing

2. Then navigate to the folder called "Odin3_v3.09" and run the file with name "Odin3 v3.09.exe". Run it with admin rights.

3. In you phone, navigate to developer options and turn on "USB debugging and (OEM unlock (if it is there))". I am pretty sure that this option will be there. If you don't know how to get developer options, go to setting, about, and tap 3 times on the build number and you will unlock developer options.

4. Now power off your device and reboot into download mode by pressing power button, home button and volume down all together. Press volume up when you see the screen. (the screen is a blue-green colour and it says either press volume up or down, press volume up)

5. Now connect your phone to pc with usb debug enabled on phone.

6. In Odin, If you see device is added, you are good to go. If not reconnect your device.

7. Now in odin, press the button named "AP" and navigate to the "Samsung Galaxy A5 2015 Root Method" and click on the file named "twrp_20191005_a5ultexx (1).tar" and open it.

8. Now in the options section, uncheck "Auto Reboot" and check (if not already) "F. Reset Time". Leave everything else as it is.

9. Press The button "Start"

10. Wait until you see "Pass" in odin.

11. In your phone, you will see that it is "downloading" and there is a white line that is completed. Now to get out of download mode, press power button, home button and volume down all together until you see a black screen.

12. Immediately, you need to press power button, home button and volume up all together until you see the boot screen with yellow text saying "set warranty bit: recovery"

13. Now you will boot into recovery.

14. Now download "Magisk v20.zip" from this link on your pc. Link: https://drive.google.com/file/d/11O2f0HymbcVZ7hQvkGFxGHcB1ShHSr8H/view?usp=sharing

Don't extract it.

15. Now drag or copy and paste "Magisk v20.zip" to the phone's internal storage.

16. In your phone, in twrp recovery. press the install button and navigate to "Magisk v20.zip". Press on it.

17. Now swipe to install and wait a few seconds or minutes.

18. After completion, press the "Wipe Cache/Dalvik" button.

19. Afterwards, press reboot (system)

20. If you see the boot screen with "set warranty bit: kernel", you are good to go and wait till it boots the system.

21. Congratulations, your phone is now rooted!:);)

In step 20, if you see "set warranty bit: recovery" and red text above it, try this: Power off the device in twrp (recovery) in the reboot section and connect to a power supply. If you see 'set warranty bit:kernel' and a charging sign, you are good to go. You just need to hold the power button and wait till it turns off and turns on again. Just wait until it boots the system and you are rooted.