Paypal recurring payments (PayPal API subscriptions - NO WORDPRESS PLUGINS)

For our website we would like to implement subscriptions with PayPal. We would like to use the Paypal Subscription API - NO WORDPRESS PLUGINS PayPal API subscriptions - [login to view URL] - (not reference transactions) I would like to explain you our situation: We are offering a membership model on our website which currently only works with non recurring Paypal button payment. It is a wordpress website and we are using the S2 Member plugin to manage the access to certain sites according to the payments. In general, we are offering 2 different "subscription" plans. 1.) Basic Plan: A user pays 5.90€ and receives access to the content on one specific site for one month. 2.) Professional Plan: A user pays 9.90€ and receives access to all content on the available sites for one month. While the Basic Plan can be used for a one month free trial, it can only be bought for the 5.90€ after this period. On the other hand side, we want to offer discounts for the Professional Plan for longer periods (3,6 months). So in general, we need the implementation for PayPal API subscriptions - [login to view URL] - (not reference transactions) which do the following: - Basic Plan free for the first month, then automatic charge to 5.90€ a month - The free trial for the Basic plan should only be used once with an paypal email address. - Possibility to upgrade during the free trial to professional plan and to keep the free trial days (so if you have 20 days free trials left in Basic plan and you upgrade to professional plan, the 2nd payment for professional plan is due in (20+30=50 days) - Professional Plan 3 options: monthly, quarterly, half-yearly. - The option to upgrade the subscription (from Basic to Professional Plan as well from e.g. a monthly professional plan sub to a quarterly professional plan subscription). - The memberships level from s2member should remain (including EOT time) + there should be a new db field for "next payment is due") Member levels: Subscriber (standard user when you register) S2 Member Level 2,3,4.. (Basic plan) S2 Member Level 1 (Professional plan) Plans: Free trial for the Basic plan (S2 Member Level 2,3,4) for 1 month. After 1 month 5,90€ each month Basic plan - 1 month - 5,90€ (S2 Member Level 2,3,4,...) - once free trial is possible (1 month) Professional plan - 1 month - 9,90€ (S2 Member Level 1) - no free trial Professional plan - 3 months - 26,90€ (S2 Member Level 1) - no free trial Professional plan - 6 months - 49,90€