1. I don't get it. 我不懂。
2. catch your drift. 懂你的意思。
3. I don't get what you mean. 我不懂你的意思。
4. I don't grasp the meaning. 我不懂這個意思。
5. I'm not following. 我有點兒不明白,我聽不懂你的話。
I don't catch my girlfriend's drift, she always force me to join some social gathering ...I am afraid to see her...