Hi Ariadna,
Assuming you've checked that your charger is indeed working, then yes, the battery is the next logical part to suspect in a situation like yours.
The good news is that replacing the battery on your laptop is actually pretty easy compared to some. I don't have any iFixit-style step-by-step guides for you, but there's a YouTube video that shows the process pretty plainly and will easily get you through the process. If you can wield a screwdriver with any degree of confidence, you can replace the battery yourself. Here's the video.
[link|https://www.youtube.com/watch?v=polsni8iI2w|ASUS e410 Battery Replacement guide, STEP by STEP - YouTube|new_window=true]
You can search around for a replacement battery; they look to be available on all the usual sites like Amazon, eBay and AliExpress; pick one that works for you based on shipping times vs. cost; Amazon is usually the quickest but not necessarily the best price, AliExpress tends to be the cheapest but has the longest delivery times, and eBay is normally somewhere in between. Here's one of the first ones that came up when I did a search.
[link|https://www.amazon.com/ZTHY-Replacement-E410MA-EK026TS-L410MA-BV058TS-E510KA-EJ033TS/dp/B0B2JWS932|Amazon.com: ZTHY B31N1912 C31N1912 Laptop Battery Replacement for ASUS VivoBook 14 E410MA L410MA E410KA E510MA E510KA F414MA L510MA R522MA E410MA-EK026TS EK018TS L410MA-BV058TS E510KA-EJ033TS E510KA-EJ033TS 42Wh : Electronics|new_window=true]