Encrypting SD card, what happen if phone get dammaged?

When you encrypt the microSD card the encryption key that gets created is stored securely in the phone's installed operating system, and it ties the card specifically to that same phone. So yeah, if the phone gets seriously damaged or the OS gets badly corrupted you'll lose access to the data residing on the card even if you're able physically extract the card. It's essentially password-protected but the password is the encryption key, and at that point it's not available any longer.
So you need to access how you need to backup you data safely and logically. A lot of people are now denouncing online storage services because of the privacy issues involved, but do note that typically involves the free services. Pay-for solutions don't have to compensate expenses with data-mining, you're paying them for a service already. So there is that. But storing your data solely on your phone (internal storage media or microSD card) has its own risks, and it's not a reliable long-term archiving solution in any way.
Backups are really important. Set something up now. Use online storage, or use your PC or laptop if you have one, or buy a dedicated external hard drive, and then set up an automatic service, or commit yourself to manually to do on a scheduled basis (most of us won't).

A microSD card can slow down your phone's read/write (predominantly write) performance, but a lot of that is dependent on how old the card is. The problem is worse if you have a relatively dated one, not so much with newer cards. They come in varying speed classes so if your card is newer than five to seven years or so it's probably not an issue.
https://www.sdcard.org/developers/overview/speed_class/
Back in like KitKat days (2012) encrypting the storage media was a bigger issue but now smartphone hardware is a lot more advanced so any speed hit between encrypted <> not encrypted is negligible.
So the whole issue is very conditional, just use a quality, newer card.
(Newer, faster, brand name cards don't cost that much more and even then it's an investment in your data. Those really cheap, generic cards can be very problematic. it's one thing to shop around for a good deal, another to just buy the cheapest bargain-bin special.)

Kharl said:

auch

Click to expand...

?

I don't store anything even vaguely important on my phone (Or tablet), except photos which are automatically backed up to Google photos. the only other things on my phone are some mp3 files which are backed up in several places anyway.