What can i destroy the spy ships that other players are sending over to my planet if i dont want them there?

Th only way to reduce the information other players get when they deploy probes against you is to have a much higher Espionage Level than they do. Even then, they may be able to get certain amounts of information.

It's just part of the game.

wat do i need to do to destroy the spy ships? my spy ship got destroyed when i went to another player's planet to spy on them. when others try to spy on me, their spy ship dont get destroyed. do i need to send at least 1 ship out in space to patrol the planet?

Under 'Options' you can fix the number of espionage ships you will send from the 'Galaxy' screen.

The chance to destroy a reconnaisance mission depends on: 1.) the sender's espionage tech level 2.) the defender's espionage tech level 3.) the number of probes being sent (the more probes, the better chance of detection and destruction) and 4.) the level of fleet and defenses on the planet being probed (the more, the better chance of destruction).

You may need to send more probes at once to get a full report on the planet you are probing.

If you do not see a header on the report for 'Fleet' 'Defenses' 'Buildings' and 'Research', then you did not get any information there. It is possible to probe a planet, see only resources, launch an attack, and fly into a force that you don't have a chance against.

In short, it is impossible to be immune to espionage missions - only to make them more easy for you and more difficult for others. Up your espionage technology.