Hey there and welcome aboard, @user4733 
We’re so happy to know you liked our app! Thanks a bunch for your feeback 
Regarding the features you’ve mentioned, all these suggestions are already on the Wishlist. Feel free to upvote them 
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Payment through Stripe, Paypal or other services (this feature is already in works)
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Integration with Outlook Calendar to synchronize slots and add bookings to it
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Multiple appointments for the same time slot (already planned for consideration)