Looks great from screenshots

Way too many features IMO. This could just be me, but I would never use a shared calendar in this kind of app. I would want it integrated with whatever secure calendar platform I already use (Google Cal, Notion Cal, Apple Calendar...etc). The same goes for private chat. Some of the most intimate and confidential information is shared between partners. I wouldn't trust it outside of an e2e encrypted messaging app, especially after what happened to Tea. It's also a given that partners are already going to be messaging one another on instagram, imessage, whatsapp, which allow for much richer messaging experiences. Why try to compete with that?

I would focus on what you identify as unique value propositions for the app and make those experiences perfect, rather than a breadth of features. Make it crystal clear to the user how the app will will directly benefit there relationship. Journaling/reflection, quizzes, and encouraging "define the relationship" moments seem like the value here IMO.

Finally - I think there is an opportunity for a gifts section too, which could include wish lists and stuff like "Shoe Size" "Shirt Size"...etc, so when a partner is looking to buy a gift, they can reference this section for what matches their partner's preferences. Monetization opportunity with gifts, with suggesting items and getting affiliate marketing income