Do you use nail to press on some fingers?

[Mystery123]

So we are supposed to press with finger tips but the index finger tip never is parallel to strings.
When I look at my fingertips, index finger has callous mark that's like 45 degree angle.
Middle finger almost good but still little bit at a tangent.
Ring and pinky are perfectly straight as they should be.

When playing D chord, my index is always at an angle so that the string is almost at half of the nail position.
Middle finger nail is just at the corner of string.

Do you have index nail completely parallel when playing any chord, specially D?

[rick-slo]

Not much choice when you wrap your thumb around the neck like that. OTOH if your fingertips are not bumping into other strings then fine.

I keep my thumb behind the neck most of the time.

[JonPR]

Originally Posted by Mystery123

So we are supposed to press with finger tips but the index finger tip never is parallel to strings.
When I look at my fingertips, index finger has callous mark that's like 45 degree angle.
Middle finger almost good but still little bit at a tangent.
Ring and pinky are perfectly straight as they should be.

When playing D chord, my index is always at an angle so that the string is almost at half of the nail position.
Middle finger nail is just at the corner of string.

Do you have index nail completely parallel when playing any chord, specially D?

The "parallel" idea you mention is really only when playing scales, or anything where each finger has its own fret. I'd call it fingers parallel with the frets (i.e, if you were to lay them flat across the fretboard). And that's still only really a practical ideal when playing around the middle of the neck.

But various chords (and lead phrases come to that) require different fingers on the same fret, which means the angle has to change. Typically the fingers then approach around 45 degrees to the frets.
The critical point is that the last finger joint should - as near as possible - come down at right angles to the fretboard, because that's the most efficient use of pressure, and also helps you avoid neighbouring strings. Naturally that's not always possible: for any particular chord, some fingertips may be upright that but others won't.
E.g., when I play a D chord, my middle and ring fingertips are upright relative to the fretboard, but the index is leaning back just a little. In your photo it looks like your middle tip is upright, but the others (especially the index) are leaning back a little. That's not a problem, provided your ring finger doesn't touch the 1st string.

[Gitfiddlemann]

As mentioned, I think it depends on the chord. But imo you should really try to free up your hand and give it some space.
For example, unless you're fretting an F#, or purposely muting on the 6th string, your thumb has no real purpose up there. It's making it more difficult for the rest of your fingers to play with as little pressure and tension as needed. Note how flat your index finger is. You want to avoid that kind on unnecessary tension wherever possible.
I try to play D chords like this, (as Rick mentioned, with thumb on back):

It's less tension on the hand.

[beninma]

I've dealt with some middle finger/fingernail issues with D.

I keep my nail on my middle finger shorter than you do.

One thing that helps with getting the fingers more parallel is realizing it's totally fine on a D chord with standard fingering for your middle finger to come in contact with the 2nd string. It won't mute it because you're fretting the 2nd string with your ring finger one fret up. Realizing that gives you more flexibility in positioning the finger to get the 1st string away from the nail and avoid the nail hitting the fretboard.

When I first started I was trying really hard on all chords to keep a finger from touching any string except the one it was fretting.. it makes it harder than things need to be. My teacher worked that out of me pretty fast although I had to figure it out myself for the D.

[Mystery123]

Thanks for replies.
Fingertips don't touch other strings so that's fine there.
As for thumb, I find it easier to play some chords like D and C and can mute the 6th string so it doesn't add bass note when strumming.
For other chords like G, I have thumb on the back.
I tried briefly playing D with thumb on the back and it felt awkward.
I guess I need to practice that more.

[SunnyDee]

The scale length is too long for me to put my index finger perpendicular to the string when near the nut and reaching across 3 frets, like with an open C in standard, so, me, too, my index callous is at an angle. I can't reach my thumb over, ever, so that's not a factor for me.

[JonPR]

Originally Posted by Mystery123

Thanks for replies.
Fingertips don't touch other strings so that's fine there.
As for thumb, I find it easier to play some chords like D and C and can mute the 6th string so it doesn't add bass note when strumming.
For other chords like G, I have thumb on the back.
I tried briefly playing D with thumb on the back and it felt awkward.
I guess I need to practice that more.

Personally, I'd say you need thumb over on D, at least if you're strumming, in case you hit that 6th string. (The 5th is no problem.) Personally I'd only play D with thumb on back if the surrounding chords were easier that way, and I was playing fingerstyle, where an unmuted 6th was not an issue.
For C, I often play a 6-string C/G shape (3-3-2-0-1-0), which suits almost any eventuality, strumming or picking.