No expert here, why can't I make sound louder w Audacity 333?

I have an old radio program. I opened it in Audacity 3.3.3 on my 19,1 iMac w Sonoma. The volume or loudness, whatever its called goes up then down then back many times. I go to Effect/Volume/Amplify - but the number is 0.0. Audacity will not increase the volume. If I go to Effect/Volume/Loudness Normalization - 0.0, & Normalize is - 0.1 which reduces the sound.

So how do I increase the loudness of this file? Is there a way to increase the sound without creating clipping? Like is there a way to target lower sounds of a file only?

(soft) Limiter with make-up gain.

Upwards compression . Audacity’s compressor is downwards type, but worth a go, again with make-up gain on.

T,

What does upper or lower compression mean?

JohnR

I did give a Wikipedia link to a diagram …

Dynamic range compression - Wikipedia #

Downward compression makes loud sounds quieter,
Upward compression makes quiet sounds louder.

An infamous Upwards and/or downwards compressor plugin is Xfer’s OTT (free)