Well, you could simply buy new, better, louder earphones. F.ex. the KZ-E10 TWS earphones with 5 drivers each. They blow up your ear if you move the lever to more than 2/3 and are quite cheap but comparable to 500€+ stuff. They sound fantastic. Just a recommendation.
Each earpiece is equipped with 1x 10mm double magnetic dynamic driver, 2x 30095 balanced armature drivers and 2x 50060 BA. In additions to this, this model carries a Qualcomm QCC3020 chip with Bluetooth 5.0 tech.
For 50€ you won’t find anything near it. And: they are really, really loud and sound fantastic.