Learn Spanish (Latin America): Vamos a visitar un bosque más grande que este parque. - We are going to visit a forest larger than this park.

In Spanish, to say something is "larger" or "more [adjective]", you put más before the adjective and que after it. So, "larger than" is literally "more large than" (más grande que).

Would grande change if we were comparing a feminine noun instead of a masculine one?

No, it stays exactly the same! Adjectives that end in -e in Spanish, like grande, do not change to match masculine or feminine nouns. They only change when talking about multiple things (adding -s to make grandes).

Why use vamos a visitar instead of a single future-tense verb?

Using vamos a plus a basic, unchanged verb like visitar is the most common way to talk about future plans in everyday Spanish. It works exactly like saying "we are going to visit" in English.

Why is it este parque and not esto parque?

Parque is a masculine word. When you point out a specific masculine thing to say "this [item]", you use este. It is a common trap to use esto, but esto is only used for vague or unknown things, like asking "What is this?".