You have several weapons in your Armoury to defend against a trump contract - Leads, Distributional (Count) Signals, Attitude Signals & Discard Signals.
DISTRIBUTIONAL (COUNT) SIGNALS
Use distributional signals to show how many cards you have in a suit. Again, don’t play a card without a reason, look out for signals and play as a team.
An attitude signal usually occurs when we lead an honour. A high card from partner suggests they like the suit while a low card suggests the opposite. Again, don’t play a card without a reason, look out for signals and play as a team.
If Declarer is running a long suit or drawing suits, you will run out and have to play a discard. Your first discard is a signal to Partner to indicate your preferred suit so that it can be led back at the next opportunity. HELD (High to Encourage, Low to Discourage) is a popular system. Again, don’t play a card without a reason, look out for signals and play as a team.
There are many more sophisticated Discard Systems. As you develop your game, you and your partner will decide which one you like best. One of the simplest is Dodds - ODDS OR EVENS. Discard an EVEN card of a suit you want led back. An ODD discard shows preference for the other suit of the same colour as the discard.
2H - I prefer hearts
3H - I prefer diamonds
3C - I prefer spades