"Estamos aprendiendo mucho con este diccionario."
Translation:We are learning a lot with this dictionary.
I don't know the technical reason why you can't use 'much' here but it's not good english. It's interesting because you can use 'much' if this sentence is in the negative: "we aren't learning much with this dictionary".
i think that for the most part much is reserved to negative form, such as not much or not so much, or not too much
I get that 'con' means 'with', but doesn't something like 'we are learning a lot from/by (reading?) this dictionary.' sound better?
I wonder when to use Yo aprendo and when to use estoy aprendiendo since they both can mean I am learning
You would use 'estoy aprendiendo ' when you are busy learning with the dictionary in your hands at that very moment.
'Yo aprendo' is more for when you are learning in general. Like, I am learning Spanish, but at this moment I am mucking about on the forums, so it is not 'estoy aprendiendo'.