Yes they are, to be more exact Love like the galaxy S1 and S2 together is one big story. China’s law limited the # of episode per season but because the director didn’t want to rush through that novel that it was based on he found a loop hole decide to split it into 2 season (if you think about it, usually season 2 take a year or 2 to be produced after the first season but for Love like the galaxy, S2 was aired almost right after S1 was finished airing). Hope that helps with your confusion :)
The director for this show is really adorable and a big fan of the main couple like the rest of us :) (if you’re interested there are some behind the scene clips that you can watch on youtube). He pays a lot of attention to details and really respectfully to the novel (almost recreating the exact details in the novels). I haven’t read the novel myself but I can tell that he put in a lot of thoughts to every scene.