I used the puzzles provided by lichess themselves. So, could be problem in my code. I will work towards making it more difficult and letting users choose the level of difficulty. Thanks for the feedback!
Ok, if you're just using the lichess puzzles and stockfish, why wouldn't I just go to lichess?
Okay its not just about the puzzles, I built it primarily for the game review that chess.com charges money for. And with the use of stockfish I've tried to make the UI more user friendly especially for beginners who want to study openings and just spend time looking at a chessboard making moves and seeing what is the best move for each position plus its easily accessible for a newcomer. By contrast, in lichess you have to go through the learn page and "find" the study page while in ChessDream you just go to the page and start making moves. I'm not saying my site is better than Lichess; I'm just proposing my opinions about how ChessDream might be helpful for people that are willing to learn chess.