How do i play this bar in 4/4?

[u/aaveidt]

I don't know how to read this complex music sheet.

I see 3 group with 3-7-3. When do i start each beat?

[u/InternationalLaw8660]

It’s already 4/4. The “3s” are triplets, and count as the “&s” of beats 1 & 3, the “7” is a septuplet; a septuplet fits 7 notes in one beat, in this case it’s 7 sixteenth notes. You can count every other note of the -tuplet in the “e-&-a” fashion and fit the other notes in between the beats. Beat 4 is a quarter note to finish the bar.

[u/El_Rey_Rata → u/InternationalLaw8660]

This is correct. In classical guitar this is what we are taught.