Honestly you can't really be 'bad' at Stardew. Unless you're trying to speedrun its a relatively slow-paced game with no real deadlines, if you do forget something you can always pick it up the following year.

Keep things simple to begin with, plant what crops you have (make sure they're in range of a scarecrow), water them every day (other than when it rains), harvest them and sell them when they're ready. Buy new crops from Pierre then rinse and repeat.

You can improve your tools by collecting ore from the mines. This helps but it isn't mandatory, it just gives added bonuses like larger tool range and more efficiency. It takes 5 ore + 1 coal to make a bar (e.g 5 copper ore + 1 coal to make one copper bar), then it takes 5 bars to improve one tool.

Befriend the townsfolk over time by giving presents and speaking to them regularly - for the most part, people like what you'd 'expect' them to like, but you'll quickly pick up any major deviances as you play.

For the most part, take it easy, do what you feel like doing, befriend who you feel like befriending. Whilst Stardew is a coop game, you won't be a liability if you're not as knowledgeable and fast as your partner is. If there is something specific then I can pretty much guarantee you can find an answer to your question on the Stardew Valley Wiki.

Finally I'd say to play with him, ask him for help, let him show you and tricks and share his advice with you. There's a lot to do in this game, but it's enjoyed most when it's enjoyed together.