Innertube patch don't seal for long I'm quite new at biking and I got my first flat yesterday. I was able to remove the inner tube and patch it, thanks to a lot of youtube videos. But today I found the tire without pressure. And I found that the patch was leaking. I replaced the tube with my spare one. But I want to know if this is normal, for a patch, to last a few hours and then unstuck itself and let air pass?

Thanks
Self adhesive patches are less reliable. I carry them (because they are so small) with my spare tube with my tubeless tyres to get home when the crap hits the fan but I witnessed some repeated struggle with some. I cannot comment your particular brand but my colleague had to re-apply some every 20 km or so. 

I would use them to get home when the spare tube got punctured too. To permanently repair a tube use the traditional patches with a vulcanizing glue.

On my bikes that use inner tubes I carry the traditional patches. I want the reliability of those and have the space for them.