I agree the brown chairs are too much brown. Of the chairs you show, I like either the orange or blue (based on whatever your color scheme is) and the slight tufting adds some interest. The sea-green chair has too much tufting going on for such a simple table. Actually, the maroon chairs aren't bad, but, doesn't give much contrast to the brown table, IMO, but would work fine. If they are RED, then that's a better contrast. Have you checked the inside leg dimension on the table to ensure any of the optional chairs will fit with enough comfort space (elbow room) for the sitters if you are putting 2 chairs per side? This may help with your decision.

I would love to give more modern look to this dining room. What should I change and add to it? All advices are appreciated. Thank you.

Nice! I’m liking the suggestion of gray or black chairs after seeing your photos, for contrast. I’m not sure of budget, but Overstock, Wayfair, etc are having really good holiday sales right now. Your table looks very neutral, should mix well with nearly anything.

How many people will be eating at the table on a regular basis? Are you removing the other window coverings because I think they look nice and relate well to the living room. One suggestion would be to have bench seating under your crosses (please keep them) with a narrow long rectangular table and 2 to 3 chairs across from the bench. It would tuck it closer to the wall so you have walking space. You could then put china cabinets or bookcases on either side of the door. Another suggestion would be to set up a table that goes from a console to a table to sit 8-10 peopls. You could set it up as a desk for everyday. It's a hard room because of the doorways.