Arduino with MCP2515 as a controller

I have an Arduino and an MCP2515, and I'm using this library:
https://github.com/coryjfowler/MCP_CAN_lib
I can also receive data, but how do I compare it now?
Assuming we receive the message with ID=25A and Message=5,5,5,5,5,5,5,5.
Now, I want to execute some code.
I only ever find examples of how to set the internal filter.

I haven't quite understood the problem yet. You are receiving a CAN frame with corresponding data, and you want to perform some action based on that data?

I assume that you have received the data correctly and are caching it for further use. Then you can query them using a regular conditional statement.

Okay, gib mir den deutschen Text.

if (Byte[0] == 0x01h)
"Please provide the text you would like me to translate from German to English."
do something if the first byte of the CAN message contains a 1...
Bitte gib mir den deutschen Text, den du übersetzt haben möchtest.

Sure, here's the translation of the German text into English, with double equals signs for "C":

"In C, please use double equals signs."

if (Byte[0] == 0x01h)
Bitte gib mir den deutschen Text, den du übersetzt haben möchtest.
Do something if the first byte of the CAN message contains a 1.
Bitte gib mir den deutschen Text, den du übersetzt haben möchtest.