Start with a decodable original
All audio tools export 44.1 kHz, 16-bit PCM WAV. Browser codec support varies, and the total decoded duration is limited to three minutes. A small compressed file can still be too long; converting to WAV does not recover detail lost by compression.
Build the sequence before changing gain
Trim unwanted ends and join clips in selection order. Joining is sequential, not a mix of simultaneous tracks. Add fade-in/out within the final duration, and review mono conversion because opposing stereo phases can cancel sounds.
Listen as well as reading the numbers
Gain changes sample amplitude and can clip peaks. Peak normalization targets the loudest sample, not integrated LUFS loudness, and can raise background noise. Listen to the exported WAV on the intended playback device and keep the unedited source.