Formal:
* Ek sal jou altyd met my hele hart en siel liefhê. (This is the most literal translation and is very formal.)
Informal:
* Ek sal jou vir altyd liefhê met my hele hart en siel. (This is more informal and is commonly used.)
* Ek sal jou vir altyd liefhê, met my hele hart en siel. (This adds a touch of emphasis and is slightly more romantic.)
* Jy sal vir altyd in my hart en siel bly. (This translates more to "You will always remain in my heart and soul" and can be used as a powerful expression of love.)
More poetic/romantic:
* My hart en siel behoort vir ewig aan jou. (This translates to "My heart and soul belong to you forever" and is a very romantic phrase.)
Ultimately, the best translation will depend on the context and the intended recipient.