Raise the back of your tongue to touch the soft palate (velum). Stop the air, then release.

Americans pronounce companies as KUHM-puh-neez (/ˈkʌmpəniz/). Stress falls on the first syllable — keep everything else short and quick. You'll hear it in sentences like "The merger between the two companies created the largest bank".
Record yourself saying "companies" and play it back. The mic stays on your device — nothing's uploaded.
3 syllables, 8 sounds. Tap a syllable to jump to its row, then explore each sound's mouth shape and how it's made.
The schwa before N disappears — N becomes the vowel of the syllable. Go straight from the previous consonant to N.

Pull the corners of your lips back slightly. Arch the middle-front of your tongue high toward the roof of the mouth.

Same position as S, but add vocal cord vibration. Feel the buzz.

The textbook way isn't wrong — it's just not how anyone actually says it.
Stress falls on the first syllable, not the others. Stretch KUHM — keep everything else short and quick.
Don't pronounce the first syllable too fully. The unstressed syllable reduces to a schwa — the lazy "uh" sound — in casual speech.