I can't imagine how our civilization would communicate via radio with a civilization 10-100 million years older than ours. We'd hardly even be able to absorb their knowledge (if the signal was one-way).

I think it will be a very long time, thousands of years, before we reach a decent level. But perhaps it won't be pure human intelligence, but a kind of symbiosis with AI.

There is an extremely small probability that we will find signals from a very young civilization like ours (at the level of our development in the 20th-22nd century), because these 300 years of similarity must coincide on two different planets (and the time of the emergence of a young civilization can vary greatly on different planets).