“I have graduated since 1990, then I have been married. Then I traveled abroad and gave birth.”
It does clearly express a timeline, but it’s not grammatically correct.
The first sentence states two unrelated events in the past connected with “then” as a conjunction. It seems to be in present perfect tense.
This tense is mainly used to express that something has happened before now, with a connection to the present moment. For example:
“I have already eaten breakfast.” This shows that something happened before now while being connected to now.
The correct way to write your sentence this would be:
“I graduated in 1990 and then I got married.” This sentence is in the past simple tense. It shows that two separate events happened at certain moments in the past.
The other sentence, “Then I traveled abroad and gave birth”, should be phrased differently. Perhaps a better way to say it would be “Next, I traveled abroad, which is where I gave birth.” Or “Next, I traveled abroad and had my first child.” We would use a word like “next” to begin the second sentence because if we used “then” a lot it would become repetitive.
This is also in the past simple tense because the two clauses (giving birth and traveling abroad) aren’t related to each other.
The correct entire statement is, therefore:
““I graduated in 1990 and then I got married. Next, I traveled abroad, which is where I gave birth.”
