I find myself pressured to talk if the girl is not talking when on a date. Eventually so I end up on a complete tangent and start talking about the postgraduate courses offered at some university as if I am a tome of knowledge or some shit...

I know we should ride off what the girl said but when the conversation is approaching death I will need to chip in something.

TL;DR How do I create engaging conversation while not going off on a tangent when there is silence/the girls topic has died out