Study openings, particularly the more common ones. Once you're opening the first ten moves or so like a book, you'll find yourself in much better positions and will crush fellow 800s. As you find yourself in better postions, you'll get better at finding winning tactics. Good tactics flow from good positions.
Having a decent position out of the opening is irrelevant if you drop a rook as soon as you leave book. At an 800 level, it's pointless to know your favourite lines ten moves deep, as your opponents aren't going to know those lines and follow them that deep. At an 800 level, you don't need a +0.3 advantage out of the opening.
At that level, all you need from your opening is to avoid some traps and reach a playable middlegame. General opening principles will get you 99% of that without learning much in the way of specific moves. So learn some opening principles (develop your pieces, control the center, etc.), and then work on tactics.
Once you reach 1400 or so, you can start to dabble in openings a bit more, but even so your main focus should be tactics.
On second thoughts, I really doubt if people understand how one progresses from one rating to the next. Because if they did, no one would be stuck at any rating. But, most people get stuck at some rating or the other and they don't know what to do to go the next level.
As a beginner, it is hard to find a way to get improved. That's why I asked you for help when I get stuck around 800. Now my rating is 1152 in daily games. But still I feel like I am not 1152, maybe I am around 1000. (1000 is also looks like good improvement for me) because I just played 35-40 games and I need to play more games with different opponents in my level to see that I deserve this rating. Maybe I played against weak opponents, maybe they couldn't focus on game and I won. I will play more daily games, puzzles and tactics. No bullet, no blitz.
But if I get stuck around 1200 for a long time and couldn't find to way to improve, I am sure that your advices will be a bit different. We'll see
Daily games is not real chess. It's rating is irrelevant to chess skills.