Your original sentence can be corrected for punctuation and capitalization as: "Could you give me an in-depth explanation of the English grammar in this excerpt?".

Below are several better alternatives and a detailed analysis of the language based on the sources:

Better Alternatives

• Formal/Academic: "Please provide a detailed analysis of the grammatical structure found in this passage".
• Comprehensive: "Offer a comprehensive overview of the English grammar rules applicable to this text".
• Direct/Clear: "Can you accurately describe the proper grammar used in this excerpt in detail?".
• Technical: "Explain the underlying grammatical principles of this excerpt at length".

Grammar and Usage Notes

• Capitalization: You must always capitalize English when referring to the language or its English grammar.
• Grammar vs. Grammatical: While you can say grammar rules, it is much more common to use the adjective form grammatical when referring to an error or structure, such as a grammatical error.
• Explanation: Instead of an "explanation to," it is standard to provide an explanation of or an explanation for something.
• In-depth: The term in-depth is a common adjective used to describe a study or interview that finds out a large amount of information.
• Excerpt: In a technical or literary context, you might also use the terms extract or passage to refer to a short part of a larger work.
• Give vs. Provide: In formal writing, it is often better to use verbs like provide, offer, or supply instead of "give".