Girl, it's totally worth it! Seriously, it's one of the best upgrades you can do on an old notebook. The difference between a mechanical hard drive and an SSD is HUGE, like literally: with a mechanical hard drive your notebook takes like 30-40 seconds to boot up, opening Chrome or any program takes forever because the disk is making that reading noise. With an SSD you're looking at 5-10 seconds to boot, programs open in 1-2 seconds. I even recommend it to people new to the field who deal with this, because when you're rushing out for an early morning ride and come back in a hurry, that slow notebook is just way too frustrating.
Your 2019 notebook still holds up pretty well, depending on what processor and RAM you have. If it's an i5 or i7 with at least 8GB of RAM, the SSD will make your equipment basically brand new for everyday tasks, browsing, documents, videos, social media, everything runs smooth. The cost-benefit is insane, a 256GB SSD is in the 150-250 reais range, way cheaper than replacing the whole notebook. Installation is simple too if you wanna do it yourself, but it's great to pay someone to do it if you're not comfortable with it.
The only thing I'm warning you about is that it's not a miracle solution if your notebook has low RAM or a bad processor. But the chances of a 2019 notebook having those issues is low. If you wanna play really heavy games or edit video in 4K then yeah the story changes, but for normal use, web, work, studying, the SSD fixes pretty much everything that's making it slow. It'll last you a few more years easy after this upgrade.