Round your lips into a tight circle. Lift the back of your tongue toward the soft palate and add voice.

Americans pronounce whenever as wehn-EH-ver (/wɛnˈɛvər/). Stress falls on the second syllable — keep everything else short and quick. You'll hear it in sentences like "Whenever I see that movie, it always makes me laugh".
Record yourself saying "whenever" and play it back. The mic stays on your device — nothing's uploaded.
3 syllables, 6 sounds. Tap a syllable to jump to its row, then explore each sound's mouth shape and how it's made.
Round your lips into a tight circle. Lift the back of your tongue toward the soft palate and add voice.

Drop your jaw moderately. Touch the tongue tip behind the bottom front teeth and lift the mid-front part slightly toward the roof.

Touch the tip or front edge of your tongue to the roof of your mouth behind your teeth. Air flows through your nose.

The textbook way isn't wrong — it's just not how anyone actually says it.
Stress falls on the second syllable, not the others. Stretch EH — keep everything else short and quick.
Americans use a relaxed retroflex R — the tongue curls back rather than rolling. The R is one continuous sound with the vowel before it, not two separate sounds.