MrWaliglobal wrote: "...but it will slow down my Device? right ?"
Besides the temporary slowdown that Mac described, there's another — resulting from the original battery still being in an old model iPhone such as your XS...
The long process of applying an iOS update to an iPhone with a weak, aging battery can be the proverbial "straw that broke the camel's back." In that case you may see not only slowdowns, but glitching also — often mistakenly attributed to bugs in Apple's iOS update. So...
Does your iPhone XS still have its original battery?
And what's the Maximum Capacity % here?...
Settings > Battery > Battery Health
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