My parents are not shomer Shabbat and spend all day watching tv or playing on their phones. How can I talk to them while observing Shabbat? What should I do if I’m the only person in my house observing?
This is quite literally the situation described in Vayikra 19,
אִ֣ישׁ אִמּ֤וֹ וְאָבִיו֙ תִּירָ֔אוּ וְאֶת־שַׁבְּתֹתַ֖י תִּשְׁמֹ֑רוּ אֲנִ֖י יְהוָ֥ה אֱלֹהֵיכֶֽם׃" You shall each revere his mother and his father, and keep My sabbaths: I the LORD am your God." (Remember that the vav in Hebrew is just a connector, this passuk could also be translated as "You shall each revere his mother and father but keep My sabbaths)
Try to smile and gently remind them you can't do X activity because it's Shabbat. Don't pressure them to do the same, just remind them that you yourself can't do it. Will they allow you to light Shabbat candles in a corner somewhere and make kiddush over grape juice? Doing these things unintrusively and not nagging them to get involved could go a long way.