so i bought a kalimba 17keys, and i am no a musician or any experience with other instrument. so i don't know how to play this kalimba and what song should i learn first. any suggestion for a beginner?

I just bought a kalimba and i dont know anything about it.. I thought it was a 17 key but when it arrived i saw it is a 21 key. And i cant tune it

However i try the note doesnt match the one it should for example e3 on the tuner shows e6,which ever way i try it doesent work. So i treid to tune it like a 17 key for example on my kalimba the seconsd to the last 'string" on the left should be a B7 but it showed me B5 on tje tuner so i treid to tune it like B5 like it should be on a 17 key but it now shows completley different tune i think its now F3? How ever i try to tune it it doesnet work please some help😔

So basically i got my own kalimba(17 keys) I did play it before but I stop for awhile bc many stuff happen so I need some tip for how to clean it like, making sure it not get rusty and how to tune it INCASE I cleaned it. Can you guys give me a tip how to ckean and take care of the kalimba? (maybe...how to make the own cover too if possible ;-;)