Most of the time I can't keep the things I bought in theira decent state. Most of the time I can't keep the things I bought in a decent state.

Alternately, "in good condition."

Most of the time I can't keep the things I bought in theirthat I buy in a decent state. Most of the time I can't keep the things that I buy in a decent state.

I think it's better to know how to treat your your belongings well so you couldan sell them later. I think it's better to treat your your belongings well so you can sell them later.

Instead of throwing away a thing,things away and adding your garbage to the junkyards, which are already full. Instead of throwing things away and adding your garbage to the junkyards, which are already full.

This sentence is incomplete, but you can combine it with the previous sentence since they are contrasting two behaviors. "Of course, it's more ethical to do this instead of throwing things away and adding your garbage to the junkyards, which are already full."

Unfortunately, in our country, we don't have a garbage recycling system, so reselling stuff is the a good way to do. Unfortunately, in our country, we don't have a garbage recycling system, so reselling stuff is a good way to do.

I bought it when I was at high school. I bought it when I was at high school.

I bought it when I was atin high school. I bought it when I was in high school.

I didn't know how to treat it well, and it ended up being broken and dirty, and I droppedquit playing it. I didn't know how to treat it well, and it ended up being broken and dirty, and I quit playing it.

I think "quit" is more natural, but "dropped" is also okay.

Eventually, I'm glad that my guitar is now in good hands, and is bringing entertainment to someone, rather than lying broken in the dust. I'm glad that my guitar is now in good hands and is bringing entertainment to someone rather than lying broken in the dust.