PLEASE I NEED HELP (if you need help also, i can help you after!)
I suggest you edit your post to put it in the TPS sub-category for your platform if you want someone to join your game. It would also help if you said which mode (normal etc) and level you are.
If you look through the TPS Discussion category, you’ll also find plenty of threads about RK-5 full of tips for defeating it - definitely doable solo unless you are severely underlevelled for the fight.
What platform are you using so I can get you moved to the right place and so you can get help quicker?