I read a suggestion previously that da makes the following verb passive. So, in this sentence instead of reading it as We have much to offer, the da makes it read, We have much to be offered. Whether this is true or not I don't know. And why would you want to make it passive, and why this verb as opposed to another, I don't know either, but something to consider.
I was marked wrong with "We have many to offer." "much" (so much) and "many" are very similar. In English, the "many to offer" would apply more towards physical things (like toys), whereas "much to offer" would apply more towards non-physical things (like skills). In what way was my response incorrect?