i dropped my sens in val from 30cm/360 (originally mirrored from tf2) to 65 and it was like night and day i felt like i actually had the control to click heads, just gotta commit to getting used to a new sens.
when i first dropped my sens in tf2 from 17 cm to 30 cm it felt like i could never figure it out, but a month of surfing and pubbing/pugging and it was already pretty comfortable and i felt the benefits of more control playing hitscan classes.
tldr; it'll suck at first but give it a month or two and you'll feel the benefits of the added control.
for val specifically people generally recommend having very roughly an effective dpi (edpi) between 290 and 320 ish, which is just a calculation of in game val sens * mouse dpi. so mine is at 200, which is = 0.125 * 1600, or ~65 cm/360