First of all, sorry for the general context of the question but I’m very inexperienced. I hope I'm not breaking the rules.
Simplifying, in the short sci-fi novel I’m writing there’s a super-intelligent alien probe that wants to communicate with us. It can intercept all of our communications leaving the Earth so it chooses to send a signal to the ESTRACK (or one of the other deep space networks).
Let’s say that the probe wants to send a simple “text” message, maybe a “do you copy?”. If it’s starting to learn English, to grease the wheels, how can it do it? What kind of... “format” would the signal have to be received and understood?