Questions & Answers about Мой папа часто вспоминает о старой работе.
Why do we use о here instead of об for "about"?
We use о because the next word, старой, starts with a consonant. You would use об if the next word started with a vowel sound (like об этой работе - about this job) to make it easier to pronounce.
Why is the phrase старой работе instead of старая работа?
The preposition о (about) requires the Prepositional case. The dictionary form for the noun is работа (feminine), which changes to работе. The matching feminine adjective старая (old) changes to старой in the Prepositional case.
The word папа ends in -а, which usually makes a word feminine. Why does it use the masculine word Мой?
Words that refer to male family members, like папа (dad) or дедушка (grandpa), are masculine because of their meaning, even though they end in -а. Because it is a masculine noun, it takes the masculine modifier Мой.
Could I use помнит instead of вспоминает here?
It would change the meaning slightly. помнит means "remembers" as a continuous state (having the facts in his memory). вспоминает means "recalls" or "reminisces" - the active action of bringing it to mind, which pairs perfectly with the word часто (often).