A thesis statement, in other words, is only one sentence, not two or three or more. Because the thesis statement is the main point you want to make in one essay; so it should be one sentence.
first you have your title on what your going to write.
Next you write what your going to write about on a new paragraph that you need to write when it happens and why it happens. Either can be correct depending on the context and the tense. I will write you means the same thing as I will write to you.
Whatever kind of essay you are writing, you want to decide before you finish it what the point will be, where it's going.
Thus you want your thesis statement to express in a sentence what your whole essay says, what you want your readers to know or believe or understand by the end of the essay.
Thus every good essay has a thesis statement, though it may be implied rather than explicitly stated in the text of the essay.
If you are writing a primarily "informative" essay rather than a primarily "persuasive" essay, that doesn't mean your essay doesn't have a thesis; it just means that your thesis is a statement about which your readers are uninformed, rather than one on which they may have opinions that differ from yours.
The only reason for asking for a trial thesis statement is to allow us to have something to discuss in class.
You will usually not finish writing your thesis statement until you have nearly finished writing and revising your essay.
You may have been asked in a previous class to put your thesis statement in the first paragraph of your essay.
There is nothing wrong with putting the thesis statement in the first paragraph, if that will help you to get your point across to your readers.