Why to defeat the 1000 engine I had to practice a month?

Really, this engine isn’t hard for me now. But it was late February, and I trained whole March.

I coached a high school team where players played in live tournaments and began around 700. Some increased to 1000 in several months, some took much longer.

Those who increased faster studied their games, looked at why their mistakes were bad moves, and also studied basic play books. They also learned you must attack and keep pressure on your opponent to win - playing too defensively loses games.  A good and legally free book for players around 1000 is Jose Capablanca's Chess Fundamental: https://www.sources.com/SSR/Docs/Capablanca-ChessFundamentals.pdf

If I was still coaching a high school chess team, I would give every player this book, make them read it, and quiz them:

Fred Wilson, Simple Attacking Plans – four straightforward principles demonstrated with 36 annotated games.  He writes:

I have come to believe there are only four essential, even primitive, concepts which you must learn and understand in order to play successful, attacking chess - Fred Wilson

1. In the opening, whenever justified, relentlessly attack the weak squares f7 or f2.
2. Most successful kingside attacks are directed against the squares h7 or h2, and they are often preceded by eliminating or driving off its defender. Corollary: most successful attacks require a long queen move.
3. If your opponent’s king is trapped in the center, make every reasonable effort to open and dominate the e-file, and sometimes the d-file also.
4. If possible, point all your pieces at your opponent’s king.