The underlined portion of the sentence should be fixed to:
First, we'll try to fly the kite. Later, we can attempt to hike up the mountain.
To fix the punctuation and capitalization errors, we need to make two changes:
1. Capitalize the word "First" to start the sentence.
2. Add a period after the word "kite" to end the first part of the sentence.
By making these changes, we separate the sentence into two distinct thoughts or actions. "First, we'll try to fly the kite" represents the first action, and "later, we can attempt to hike up the mountain" represents the second action.
It's important to use correct punctuation and capitalization in writing to ensure clarity and proper grammar.