Is someone targeting my questions and downvoting them all? Basically all my questions have downvotes.
Is someone targeting my questions and downvoting them all?
I don't think that anyone will target somebody else's question and downvote them. There's a script that runs every day that'll check for unusual voting activity and invalidate it automatically. So generally, when you see something odd, give it a day and see if it clears up. If not then it probably means something is wrong with your question. Try to ask for clarification. Sometimes (or maybe most of the time) people might not give a reply but this is the only way.
Now, let's talk about why your questions have downvotes.
Is there a strategy to win chess960 games? Your this question was a duplicate which means you didn't go for enough research.
What openings are best for white or black in fast games of chess The reason was already specified that it was an opinion-based question.
Is it possible for black to win this? Well, this question wasn't interesting at all. You just gave a puzzle and asked for the best solution (which is right according to me). The problem was that it wasn't a really good puzzle. One could have easily turned on the engine and found the answer. As @PhilipRoe commented on it To make a claim on other people's attention you should be sure that it is interesting.
How would you feel if everyone else starts posting questions like the best way to finish the game or find a mate in 11?
How to learn endgame theory This one is having several downvotes too. I would suggest you add more details on why your question is different from the related one, and try to explain your question more(so that the reader has almost no doubt while answering. )
I personally don't downvote questions unless they are off-topic. I hope you don't take these downvotes seriously (even though sometimes, it becomes frustrating). If your question is good you will automatically get the upvotes.
Full disclosure: the troll in me really wanted to downvote this question, just for the lolz, but I managed to resist :-).
Seriously, you can only downvote a post once. 5 downvotes and no upvotes is 5 different people telling you the same thing, that there is something seriously wrong with your post. Time to take the message onboard.
The problem you have with that particular post is that with 2 answers both with positive scores you can't just delete it. It is there for posterity.