Most of the early levels you just build up sun buy buying a lot of sunflowers and sack a lawnmower or 2 then just place killing plants and use insta kill plants like chompers and cherry bombs potato mines and squashes for the Day Levels For nights you basically do the same thing just with the night plants but since you have the free Puff-Shroom you put most of them up front so scared shrooms and fumes can do most of the damage a further back. For Roof levels you never use the catapults since they take longer to kill so starting out you mostly do the same things until you get the coffee bean then you use the Fume-Shroom upgrade plus with garlic(once you get it) to push the zombies into certain lanes to damage all of them. I'm not the best by any means and have only ran the game twice but These are the strats that most people use if you want to see more details about certain levels I would watch Supers 2nd place run or watch him on twitch He talks during most of it so if there is any more questions you can ask during his streams

One thing that should be worth keeping in mind is that once you've spawned a new wave of zombies, the old wave of zombies doesn't affect zombie spawns at all anymore. This can lead to situations where a lawnmoower can be even more efficient than usual. For example, if two regular zombies spawn on wave 4, you only need to kill one of them with e.g. a Squash, and the spawns will immediately proceed while the other zombie makes its way into the lawnmoower.

And also, in general, unless the last spawned wave was the 9th, 19th, or 29th wave in a level, the next wave will always spawn immediately if you reduce 50% of the most recent wave's current health. This means, for example, that you want to (often) focus down coneheads moreso than regular zombies, and that you don't have to invest a whole lot of resources into damaging a conehead quickly if he has already lost like 40% of his HP and isn't going to eat your plants

• Be reactive with your firepower and conservative with your expensive instants (chompers, cherrybomb). Spam cheap instants (potato mine, tangle kelp) on cooldown, saving them for a short amount of time when that will generate much better value (e.g. wave 9).
• Try to count to 9 waves (or for the first flag, 3 waves of size 3) and try to save resources (e.g. cherrybomb cooldowns) for reducing that wave by 100% as fast as you can.
• Get a feel for when you should pause sunflower placements to keep sun ready for firepower (typically, less than 10% of the time until you have 10-20 depending on the level).
• Try to learn typical openings, sunflower totals, and damage setups for each level - you can do that by watching runs.
• You can use wall-nuts to stall out a zombie at a lawnmoower, only letting it loose once another zombie spawns in that lane.
• Place the third puff-shroom reactively. Puff-shrooms mostly belong on the 7th, 8th, and 6th columns, counting from the left. The first two puff-shrooms can go into the column 8 spots of rows with a grave on column 7 and no grave on column 6.

As the others have said, the primary way to save time in PvZ isn't "planting faster" or "menuing" but rather making good decisions on how best to spend (plant) your limited resources (sun). There is a constant tradeoff between economy (sun production), killing a particular wave quickly (instants like chomper/squash/cherry), and DPS over the course of the level (peashooters, scardies, and gloom). There are also small instances of RNG that effect the optimal decision on any wave. Because the game is non-deterministic and different zombies appear in different rows every time you play through the game, it is impossible to come up with a single route that will work every single time. Rather, you have to react to what the game gives you, and learn how to deal with good and bad RNG effectively.

I highly recommend taking some time to watch our Any% tutorial and applying its principles to your game play. Start with memorizing what plants to take in what levels and approximately how many of each plant type to plant every level. Once you have that down, work on trying to make each wave faster via the 50% rule, especially the 9ths and final waves, and minimizing the number of very slow waves. Join our discord to get further advice.

Here is the most current and most detailed video tutorial: https://www.speedrun.com/pvz/guide/npp9u

Happy planting!