Ok, you need to sort out the crashes, they sure spoil any game.
My first thought on this is a factory reset, it could cure the problem, but in any event, it will do no harm and should improve the way the game performs generally.
Down grade the graphics if they are on high. You can always restore them if you do not think they are the problem.
Run a malware program such as Malwarebytes which is free to download and will remove any background programs which may have crept on to your machine.
Do a general clean-up of your computer using the systems tools. Remove all games that you no longer play. Clean out the temorary files, cookies, and recycling bin. Then do a defrag. This should make sure your computer is running as smoothly as possible.
If this does not cure the crashes, I'm afraid I can't help further. Perhaps the computer needs some general maintenance attention. Have you had it cleaned recently, you would be surprised how quickly dust can accumulate inside and how this can affect performance.
As to game play, others have given you some good ideas. My favourite though, is to work out a series of tasks, ie: complete five careers on normal lifespan, note down the time taken in sim days and weeks, then start a new sim and try to beat it. Or choose a specific trait, ie ambitious, then play twins with identical four traits. I give the chosen trait to one and leave the other with out a fifth trait. Then play them in one household, doing exactly the same things to discover how much or little benefit accrues from the trait.
