zìcóng zhīdào juānzèngdiǎn yǐhòu, wǒ méi làngfèi guo jiùwù.

Yes, both relate to time, but together they form a very common pattern:

自从 + event/time + 以后, ...

This means ever since... or since...

In this sentence:

自从知道捐赠点以后，我没浪费过旧物。

it means:

Ever since I learned about donation points, I haven’t wasted old items.

A quick way to think about it:

• 自从 = marks the starting point
• 以后 = means after that

Using both is natural and common in Mandarin. It is not considered strange or overly repetitive.

Here 知道 is best understood as learn about or come to know about.

In English, know can sound like a stable state, but in Chinese, 知道 can often refer to the moment or fact of becoming aware of something, depending on context.

So:

• 知道捐赠点 = know about donation points
• In this sentence, because of 自从...以后, it strongly suggests after I found out about donation points

If you wanted to make the idea of finding out even more explicit, Chinese might also say:

• 自从知道了捐赠点以后...
• 自从了解到有捐赠点以后...

But the original sentence is fine.

Yes, it can.

知道 + noun often means know about + noun.

For example:

• 我知道这件事。 = I know about this matter.
• 你知道这个地方吗？ = Do you know this place?

So:

• 知道捐赠点 = know about donation points

That said, in very explicit Chinese, someone could also say:

• 知道有捐赠点 = know that there are donation points
• 知道捐赠点的存在 = know of the existence of donation points

The original version is more compact.

捐赠点 means a donation point, donation site, or drop-off point.

Here:

• 捐赠 = donate / donation
• 点 = point, spot, location, site

So 点 here does not mean a tiny dot. It means a place or station-like location.

Similar examples:

• 集合点 = meeting point
• 服务点 = service point
• 回收点 = recycling point

So 捐赠点 is a place where you can donate things.

Chinese often puts time expressions before the main clause.

So this pattern is very natural:

自从知道捐赠点以后，我没浪费过旧物。

Literally, it is something like:

Since learning about donation points, I haven’t wasted old items.

Putting the time/background information first helps set the scene before the main statement.

You can sometimes move things around in Chinese, but this fronted time clause is the most natural structure here.

Because the sentence is talking about something that has not happened from that past point up to now.

In Chinese:

• 没 is commonly used to negate past actions or experiences
• 不 is more often used for habits, general truths, preferences, or future intentions

Here the speaker means:

I have not wasted old items since then.

So 没 is the correct choice.

Compare:

• 我不浪费东西。 = I do not waste things. / I’m not the kind of person who wastes things.
• 我没浪费过旧物。 = I have never wasted old items.

Here 过 is the experiential aspect particle.

It shows that someone has had the experience of doing something at least once.

So:

• 浪费过 = have wasted before
• 没浪费过 = have never wasted before

In this sentence:

我没浪费过旧物。

means:

I have never wasted old items
or, with the time phrase included,
Ever since then, I have not wasted old items.

A very important pattern is:

• 没 + verb + 过 = have never done

Examples:

• 我没去过北京。 = I’ve never been to Beijing.
• 他没吃过这个。 = He’s never eaten this.

They do slightly different jobs.

• 自从...以后 sets the starting point in time
• 没...过 says that from that point until now, the action has never occurred

So the full idea is:

From the time I learned about donation points up to now, I have never wasted old items.

That is why this feels similar to the English present perfect.

It is not just a simple past statement. It describes a situation continuing from a past point to the present.

Yes, 知道了 could also work.

Compare:

• 知道 = know / become aware, depending on context
• 知道了 = explicitly highlights the change of state: came to know, found out

So these are both possible:

• 自从知道捐赠点以后...
• 自从知道了捐赠点以后...

The version without 了 is still natural because the 自从...以后 structure already makes the timeline clear.

Adding 了 would make the moment of discovery slightly more noticeable.

旧物 means old things, old belongings, or used items.

It is a fairly general noun, and Chinese often does not need:

• an article like the / a
• a plural ending like -s
• a classifier, unless you are counting

So:

• 旧物 = old items in general
• 一些旧物 = some old items
• 这些旧物 = these old items

In the original sentence, 旧物 is being used generically, so no classifier is needed.

Also, 旧物 is a bit more formal or written than something like:

• 旧东西 = old things

It is understandable, and it means something like:

to waste old items
to let usable old things go to waste
to throw away old things instead of making use of them

The idea is probably that once the speaker learned about donation points, they stopped throwing away useful old belongings.

A native speaker might also express this idea in other ways, such as:

• 不再浪费旧物
• 不再把旧物扔掉
• 旧物都会拿去捐赠

So the original sentence is fine, but it has a slightly written or polished feel.

It could absolutely use 就.

For example:

自从知道捐赠点以后，我就没浪费过旧物。

Adding 就 gives a stronger feeling of:

• from that point on
• then
• right after that, as a consequence

Without 就, the sentence is still correct. It is just a little more neutral.

So:

• without 就 = plain statement
• with 就 = slightly stronger connection between the starting point and the result

A very natural translation would be:

Ever since I learned about donation drop-off points, I haven’t wasted any old items.

Other good translations:

• Since learning about donation points, I haven’t let old items go to waste.
• Ever since I found out about donation sites, I haven’t wasted my old things.

The key ideas are:

• a starting point in the past: 自从...以后
• no occurrence from then until now: 没...过