Tā juéde zhège wénjiàn méiyǒu yòng le, jiù shānchú le.

Here 觉得 means something like to think / to feel / to consider.

In this sentence, 她觉得这个文件没有用了 means she thought/felt that this file was no longer useful.

A helpful way to understand 觉得 is:

• 觉得 + statement
• to feel/think that ...

So:

• 她觉得... = She thinks / feels that...

It is very common in everyday Mandarin when giving a personal opinion or judgment.

这个 means this.

So:

• 这个文件 = this document / this file

Mandarin often uses the pattern:

• 这 / 那 + measure word + noun

Here:

• 这 = this
• 个 = a general measure word
• 文件 = document / file

So literally:

• 这个文件 = this + measure word + file

Even though English does not need anything between this and file, Mandarin usually does.

Good question. 个 is the most general measure word in Mandarin, and native speakers often use it in casual speech even when a more specific classifier exists.

So:

• 这个文件 is completely natural and common

You may also hear more specific forms in some contexts, such as:

• 这份文件 = this document

份 is often used for documents, reports, forms, contracts, and similar items.

So:

• 这个文件 = common, natural, everyday
• 这份文件 = also correct, a bit more specific/formal for a document

Yes, 用 is often a verb meaning to use, but in 有用 / 没有用, it behaves like part of an adjective-like expression:

• 有用 = useful
• 没有用 or 没用 = useless / not useful

So in this sentence:

• 这个文件没有用 = this file is not useful

This is a very common pattern in Mandarin.

Compare:

• 我用这个软件。 = I use this software. → 用 as a verb
• 这个软件很有用。 = This software is very useful. → 有用 as useful

This is one of the most important points in the sentence.

• 没有用 = not useful
• 没有用了 = no longer useful / has become useless now

The 了 here shows a change of situation.

So:

• 这个文件没有用。 = This file is not useful.
• 这个文件没有用了。 = This file is no longer useful now.

In the sentence, the speaker is not just describing a general fact. She is judging that the file has reached a point where it is no longer needed, and that leads to deleting it.

They do different jobs.

1) 没有用了

The first 了 marks a change of state:

• 这个文件没有用了 = this file is no longer useful now

This 了 does not mainly mean past tense. It shows that the situation has changed.

2) 删除了

The second 了 marks a completed action:

• 删除了 = deleted

So the sentence has:

• one 了 for a changed condition
• one 了 for a completed action

That is why both can appear in the same sentence naturally.

Here 就 means something like:

• then
• so
• as a result
• right away

In this sentence:

• 她觉得这个文件没有用了，就删除了。
• She thought the file was no longer useful, so she deleted it.

就 connects the first idea to the next action and often suggests that the second thing follows naturally or quickly from the first.

A useful way to think about it:

• A，就B = Because/after A, then B

Not always exactly because, but often a natural consequence.

The object is understood from context: 这个文件.

Mandarin often leaves out words that are already obvious.

So:

• 她觉得这个文件没有用了，就删除了。

means:

• She thought this file was no longer useful, so she deleted it.

Even though Mandarin does not repeat 这个文件 or say 它, listeners naturally understand that the file is what was deleted.

If you want to make it explicit, you could say:

• 她觉得这个文件没有用了，就把它删除了。

That means the same thing, but it spells out the object more clearly.

Yes.

• 删除 is a bit more formal or technical
• 删 is shorter and very common in everyday speech, especially for computer files, messages, photos, and apps

So these are both natural:

• 她觉得这个文件没有用了，就删除了。
• 她觉得这个文件没用了，就删了。

The second one sounds more conversational.

They are related, but not the same.

没有用了

= no longer useful / no longer needed

This focuses on value or usefulness.

Example idea:

• The file is still readable, but nobody needs it anymore.

不能用了

= cannot be used anymore

This focuses on ability.

Example idea:

• The file is corrupted, damaged, or inaccessible.

So in your sentence:

• 她觉得这个文件没有用了 means she thought it was no longer needed/useful
• It does not necessarily mean the file was impossible to use

Yes. 没用 is a shorter, very common spoken form of 没有用.

So these are both possible:

• 这个文件没有用了
• 这个文件没用了

In everyday speech, 没用了 is extremely common.

The longer 没有用了 may sound a little fuller or more careful, but both are natural.

This follows a very common Mandarin pattern:

• Subject + thinks/feels + clause, then + action

So:

• 她觉得这个文件没有用了 = she thought the file was no longer useful
• 就删除了 = so she deleted it

Mandarin often places the reason, judgment, or situation first, and then the resulting action after 就.

This makes the logic very clear:

1. She made a judgment
2. Based on that, she acted

Not exactly. 了 does not work exactly like an English past tense ending.

In this sentence:

• the second 了 in 删除了 does show a completed action, so the overall meaning is naturally understood as past
• but the first 了 in 没有用了 is about a change of state, not simply past time

So 了 is not just a marker for past tense. It often marks:

• completion
• new situation
• change of state

That is why it is better to think about 了 by its function in context, rather than translating it as a simple past marker.

Yes. A very common alternative would be:

• 她觉得这个文件没有用了，就把它删除了。

This version makes the object explicit:

• 把它删除了 = deleted it

The 把 construction is often used when:

• the object is specific and known
• the action clearly affects or disposes of the object

Deleting something is a very natural kind of verb for 把.

So:

• 就删除了 = natural when the object is understood
• 就把它删除了 = natural when you want to name the object clearly

Both are correct.