Either get a professional trainer for the horse or sell it and buy the one that suits both of you better (the beginner-friendly one). 5 years old is young, and definitely can be trained, but even the trained horse can be challenging for the beginner (depending on disposition, how forward the horse is, how spooky it is, and so on).
"Life isn't about waiting for the storm to pass: it's about learning to dance in the rain..."
"When we are no longer able to change a situation - we are challenged to change ourselves."
"How people treat you is their karma; how you react is yours."