not long ago i purchased 90days membership. and i wanted to expend it so i bought 1 year (+3months free)
and when i checked how many days left on the game i downloaded on ps plus for free says it got only 38 days left O_O "
iam confused so it does not stack?
Get your Portable ID!
If you check your plus membership in your services list you'll see the subscription DOES stack. For the game you'll have to renew the license by playing the game. I don't know if this can be done early or if it must be done after the 38 days but either way you'll still have access to the game.
It won't get deleted, but renewing or extending your Plus subscription won't change the expiration date of content that has already been installed, but has not expired. The license will be renewed automatically the first time that you use it after it expires, or you can manually renew it by downloading it from the Playstation Store again. The content won't actually be downloaded again if it is already installed, but the expiration date will be updated to the end of your new subscription.