Learn Turkish: Bence bu ev çok güzel. - In my opinion this house is very nice.

The word bence is made by adding the suffix -ce to the pronoun ben (I). This suffix means "according to" or "in the opinion of". So, bence literally translates to "according to me". You can also do this with sen (you) to make sence (in your opinion).

Why is there no word for "is" in this sentence?

In Turkish, simple statements describing what a third-person subject ("he", "she", "it", or "they") is do not need a "to be" verb. By simply putting the subject (bu ev) next to the description (çok güzel), the "is" is automatically understood.

The translation says "nice", but doesn't güzel mean "beautiful"?

Yes, güzel literally means "beautiful". However, Turkish speakers use it much more broadly than English speakers use "beautiful". It is the most common way to say that a place, object, or experience is "nice", "lovely", or "pleasing".

Could I say bu ev çok iyi instead to mean the house is good?

You could, but it changes the meaning slightly. While güzel focuses on the house being visually nice or pleasant to be in, iyi (good) would sound more like you are evaluating its practical condition, build quality, or value.