I want to learn English, and my dream level of English that i am seeking about is C1goal is to reach a C1 level of proficiency. I want to learn English, and my goal is to reach a C1 level of proficiency.

"Dream level of English" sounds awkward and unclear. "Goal" is a more appropriate word to describe the level you're aiming for. "Seeking about" is incorrect. "Seeking" should be followed by the object you're aiming for, but "about" is unnecessary here. The sentence would be more natural if you simply say "my goal is to reach a C1 level."

I want to learn English, and my dreamthe level of English that iI am seeking is about is C1. I want to learn English, and the level of English that I am seeking is about C1.

This is okay in the original, but "level" is a bit specific for a dream. If you want to say "dream", you can say: "I dream of reaching a C1 level in English."

.. I want to learn English and my dream level of English that iI am seeking aboutto achieve is C1. .. I want to learn English and my dream level of English that I am seeking to achieve is C1.

I want to learn English and my dream level of English that i am seeking about is C1. I want to learn English and my dream level of English that i am seeking is C1.

At the beginning of the speech. At the beginning of the speech.

The sentence is grammatically correct, but I'm not sure what you mean by it?

At the beginning of the speech., At the beginning of the speech,

Put a comma since it is not a complete sentence it is a "prepositional phrase". -> connect sentence.

At the beginning of the speech., At the beginning of the speech,

The phrase "At the beginning of the speech" feels disconnected and incomplete.