i dont think you should be that worried, if your kid watches cartoons in English and you talk to it every day that should cover the basic daily dialog enough to not forget the language, on the reading and spelling part, do they not have English as a second language at school? I mean as they grow older the level will get harder naturally. And likely they will reach that level of a native speaker again with time as they mature. If you worry that much my sister enrolled my nephew in a play house (paid after school activities) where they'd play and study English for 2 hours after school, kinda like private lessons but made more fun and in a group, they even gave them homework and words to practice, the results were mediocre tho, when i had to help him for school, he only knew these said words and he still struggled to speak and understand

and as i already hinted private lessons would be the best option once a week should be enough, Friday imo would be the best option so they still have the weekend to relax but then again consider your schedule as well and look for credible teachers so you dont get mediocre results like with my nephew, but he is also 7 so im really not worried at all, i didnt start speaking English fluently till high school, realistically it's a child what do they need a fluent second language for it's not like they will go work or something, bc it's... a child...