I have separate yearly photoshop and premiere pro plan, can i change it to one 36euro plan ?

You can't change plans.  But you can cancel your current plan and get a new one.   However cancelling early would incur 50% early termination fee.  Please read the TERMS below.

With a browser that accepts cookies and does not have script blockers, please log-in to your account portal below.  Click on Manage Plans.
https://account.adobe.com/plans
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How do I Cancel my Subscription?
https://helpx.adobe.com/manage-account/using/cancel-subscription.html
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Subscription & Cancellation Terms:
https://www.adobe.com/legal/subscription-terms.html

Hope that helps.

https://www.adobe.com/creativecloud/plans.html

Adobe Stock is 36 euro. CC is 64 euro.

(change the page to your own region)