Forgein letters showing diffrent front.

[Rokas]

Hello, have trouble with Ą Č Ę Ė Į Š Ų Ū Ž letters. (Lithuanian alphabet) Letter front are diffrent from other letter front. What to do?

[tim]

If you share a link to your store (preview link if password-protected)  it will be easier to diagnose. Most probably, your font does not have these characters. In this case, browser will use a fallback font to  render them. 

So, check the font you're using whether it actually contains those symbols.

[Rokas]

Voveriškiai LT Lietuviški mėsos gaminiai (myshopify.com) The big letters are fine, smaller ones (exemple itiems) are broken.

[tim]

Yep, looks like the font does not have those symbols -- see the diagnostics at right bottom corner of the image. 20 glyphs in Karla and 2 glyphs in Helvetica.

My recommendations: 

1. Try different fonts from the library to see if any of them has required glyphs;
2. Talk to Shopify to confirm what fonts may have it;
3. Ask a a developer to set you up with with custom fonts;
4. Finally can always fallback to system fonts in "theme settings"=> Typography; use those generic Sans-serif/Serif/Mono (bonus -- faster page loads)
   Your visitors system fonts should have those glyphs.