How do I fix this because every time I cancel a subscription to something I can’t redownload an app it makes me put in my Apple ID and fix my payment method or put a new one every time and I do it and it doesn’t work

1.

See -> If you can’t download or update apps on your iPhone or iPad

If you can’t download or update apps on your iPhone or iPad – Apple Support (UK)

scroll to point 2 & 3  ⤵️

Add a payment method

You may need to have a valid payment method on file, even if the app you want to download is free.

Add a payment method

Resolve a problem with your payment method

If your payment method has expired, declined or failed, or a message says "There is a Billing Problem with a Previous Purchase"

2. 

Follow all the steps and instructions in Related Article: If there's an issue when you redownload apps, movies, or other content from Apple

If you still need help, get more help and assistant from Apple directly, see Contact Apple for support and service -> Contact Apple for support and service – Apple Support (UK)