coach

I am not a coach, but I am self-taught/ learning from many free content. Doing the free puzzles (the 3 daily puzzles you get from the puzzles and doing survival in Puzzle Rush). The more you do this, the more your tactics get better, but also take time doing them and if you're a fast player then doubt yourself and double-check to be sure. 
Learn openings from youtubers, and incorporate them into your game if you feel confident enough to try it, or go against the bots with the openings you learned. Or use the analysis and see possible moves your opponent can play and play what the engine suggests. For instance, a complicated opening where theory suggests they play a certain move after but you may use the analysis to play what your typical opponent might play. 
Then for checkmates, sometimes it's not about constantly checking (unless you calculate that it still works etc) but forcing them into a situation in which their king is trapped or immobile or to the back rank. 
However, at this level, going standard e4,e5 then Nf3, Nc6 should be standard and into the Italian or Ruy Lopez. If they play another opening then follow it up with the standard move (hence to learn some openings that black could play against your opening) and if they play a weak move or unorthodox then develop normally. 
Even D4, D5 are viable as this could lead to more stable games if you know the opening for it. 
Take it from a guy who was like a 600 elo 6-7 months ago, and only now am I starting to play more matches. Caro Kann and E5 are the best response to E4 based on what I think, and against D4, go classical, or if you really want to then even the albin counter gambit. 

Hey i am about to start my online batch from mid of november for begginers which will be from scratch and for advance also if you are interested plzz dont hesitate to message me