Microsoft 365 features that help users manage their subscriptions, account settings, and billing information.
Judging by the price, looks like you have Microsoft 365 Basic plan, which gives you 100GB of storage.
First of all, do you use outlook.com or hotmail.com email address? You can go to outlook.com and sign in, and go to the gear icon on the upper right and go to Settings > subscriptions, expand the Email Storage section, it should look similar to this
How much are you using? If you are using more than 15GB of storage, then you don't want to go back to free account unless you can clear your mailbox to free up more space.
Then on your computer, if you go to C: drive, how much free space do you currently have?
Then go to https://account.live.com > sign in, and go to Microsoft storage, how much OneDrive space are you using now?
Once I have an idea, I can determine better if you need to keep the subscription, and if you have the option to use local space instead and get rid of the subscription.