Learn Italian: Trovo un fungo sotto l'albero. - I find a mushroom under the tree.

In Italian, subject pronouns like io are usually dropped because the verb ending already tells you who is doing the action. The -o ending in trovo makes it clear that I am the one finding the mushroom.

If I found multiple mushrooms, how would I make fungo plural?

The plural of fungo is funghi. Notice the added h! In Italian, masculine nouns ending in -go often add an h in the plural before the -i ending. This keeps the g sound hard, rather than soft.

Why are sotto and l'albero separate words? Don't prepositions usually combine with articles?

Only certain short prepositions (like a, di, da, in, su) merge with definite articles to form combined words. Longer prepositions like sotto (under) or sopra (above) stay separate from the article that follows them.

Why do we use l' instead of il for the tree?

Because albero starts with a vowel. For masculine singular words starting with a vowel, Italian uses l' instead of il to make pronunciation smoother.