grammar - How to drop a pronoun? (pronoun-dropping/removing 'I'/omitting the subject)

I wrote resume and got stuck in this place. There are recommendations to write your achievements in the short form (without "I"):

"Worked with ... "
"Created something ... "
"Collaborated with ... "

At first I wrote my resume as:

"Have created ..."
"Was responsible for ..."
"Created something ..."

Then I found out that people don't write it in such style (Am I right?).
There are three questions:

1) How can I omit "I" in the prefect tense and in the continuous tense.

2) Does this sentence "I bought potato and cooked it" work as "I have cooked potato"? (Because "cooking food" doesn't guarantee result. As I understand there is a perfect tense for this purpose.)

3) As alternative, is it correct to mix sentences as:

"I have created ..."
"Created something ..."
"Collaborated with ... "
"I was responsible for ..."

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