@Ady34 that is a lovely Acer Palmatum , they can survive for many years in the same pot but I would re pot it and cut back some foliage .
If you dont want it to grow any bigger then just use the same pot but rake out the root ball and use 50-50 cat litter soil mix.
I plant 95% of my potted plants in 100% cat litter but I am around to water every day.
Anyway you dont really want to disturb the roots at this time of year, best done in February but you can cut the foliage anytime during the growing season .
I feed my mountain maples with chicken poo, I pile in the pellets about one inch thick in March so the nutrients are washed down into the soil ready for the growth spurt in April. They I use liquid feed every two weeks until mid summer.
They hate wind, especially cold wind but are really fast growing and robust once established in the garden.
I have a couple of beautiful bonsai that I really love to stare at for long moments!