你好， 我叫Federico。呢個係我嘅作文。

Mandarin, Simplified Chinese:

你好，我叫Federico。这是我的作文。

本身 and 本來 doesn't make a huge difference in colloquial speech. In this case, 本身 is an alternative word choice to 本來.

Nevertheless, 本來 sounds more authentic.

For "to do something", you may say 做嘢. But again, it depends. 做嘢 can mean "to work", "to work on sth", "to take action (colloquial)", and so forth.

I want to do something. (implying "to do something for a purpose", say, to make her forgive me)

我想做啲嘢。

I want to do something. (anything)

我想做嘢。

However, if the verb is not a transitive verb like "talk", 嘢 doesn't have a solid meaning besides its grammatical function.

I want to talk.

X 我想講 (this expression implies that the speaking person has something else to say, translating into "I want to say, ...".)

O 我想講嘢

嘢 following different verbs has different meaning. The difference is very subtle and it really depends on different situations.

嘢 serves the function as a pronoun in the following examples. These verbs can but not necessarily follow by an object. You can translate 嘢 into "something".

I want to eat. / I want to eat something (because I am starving).

X 我想食。

O 我想食嘢。

I want to steal something.

X 我想偷。

O 我想偷嘢。

Besides, in most colloquial situations, 飲嘢 likely means drink (alcohol). If you want to say "drink something", you may say 飲啲嘢。Here, 啲 translates into "some" and 嘢 means "things".

I want something to drink. / I want to drink something. 

O 我想飲嘢 (OK but make sure the speaker doesn't really mean alcohol, lol)

O 我想飲啲嘢