I am trying to accompany a song with 3/4 time signature using guitar. There is up to four chords in one measure. I use arpeggio (1- a bass string, 2 - first three strings, 3 - first three stings again) to play it. So I suppose I should skip some chords. Which one (ones) is it better to skip? Are there any rules to do it? I should add that I play this on 7-string Russian guitar (DBGDBGD) and these chords are pretty simple here (B bemol is the only barre chord, just barre on the third fret).
Basic answer - get so that you can play it properly!
Simple fix - always play the 1st beat/chord of any bar at least. In 3/4, 1 is obviously the most emphasised, so a low G note from your example is important.The next Gm also comes on a beat (the third), so is more important than the preceding Dm, and should be played. The D7 at the end is a short note, but maybe important (can't see what follows), but because it's so different from Gm in sound and function, it really needs playing. It will probably be a sort of anacrucis (?) for a following Gm, or possibly a pushed D7, nevertheless, needs playing.
So a get out would be to play a G bass note on beat one, then a down/up strum on Gm/D7 on beat three - until you can cleanly also play the Dm as an up stroke on 2&.
Is that standard tuning for a 7 string Russian guitar? I've always had mine tuned to standard with low B, since 1965!
"I use arpeggio (1- a bass string, 2 - first three strings, 3 - first three stings again) to play it."
And there's your problem. This piece is more harmonically intricate than that. Though you could maybe get away with two bars of Dm, one of Gm. If there MUST be only one chord in a bar, the one that starts the bar is likely to be the most important.
I'm not sure if the offset of the first two Dm chords to the second beat indicates a syncopated strumming pattern or is merely sloppy printing.
I don’t trust the chords in your sheet music!
Dm should be on the first beat in measure 1 and 2. Or what do you think to play there? Ok, as you write D ... also F is possible.
Bar 3 you can let drop dm!
1 2 3+ 1 = Gm (em) 3+ = D7 (B7)
alternatively you can play gm (1 2) and Dsus7 (3)
I think the next chord in bar 4 will be gm (em).
Try out once D7 (B7) the whole 3rd measure: it will sound quite fine too, maybe not right Russian style (the 6th and 4th will only be sung in the melody).