The first sentence is well written, but you need to replace the word greatful. This isn’t a word. There is a word called “grateful” but it describes a feeling and cannot be used to describe a day. In the second sentence you need the pronoun “it” after the word leones and before is. In English we always use a pronoun before the verb, unlike Spanish. Another difference between Spanish and English is that we generally put the adjectives in front of the noun. So we would say “which is a really big forest” Thats a good use of the word really! In the last sentence you want to add the it again. “I think it was interesting” and then use the infinitive “to start” instead of stars. Overall this is very good. Despite a few errors, it is easy to understand what you are saying!