Learn Italian: Consigliamo il pesce, oggi è freschissimo. - We recommend the fish, today it is extremely fresh.

The base word is fresco (fresh). To add the -issimo ending, we drop the final -o. Because fresco has a hard 'c' sound, we must add an h before the -i of the ending to keep that hard sound. Without the h, the 'c' before an 'i' would make a soft 'ch' sound.

Can I say molto fresco instead of freschissimo?

Yes, molto fresco (very fresh) means the exact same thing. Adding -issimo to the end of an adjective is just a very popular and natural way in Italian to express that something is extremely or very much that quality.

Where is the word for 'we' in the first part of the sentence?

It is built directly into the verb! The -iamo ending on consigliamo tells us the subject is noi (we). In Italian, you usually leave out subject pronouns like noi unless you want to add special emphasis.

Is pesce singular or plural here?

It is singular. Unlike the English word 'fish', which can be singular or plural, the Italian word pesce is strictly singular. Its plural form is pesci. Here, the speaker is recommending il pesce as a general category of food on the menu today.