Me dejé el paraguas en la cafetería.

Here me is part of the very common Spanish pattern dejarse + object, which often means to leave something behind / forget something somewhere.

So me dejé el paraguas does not mean I left myself the umbrella. It means I left my umbrella behind.

The me matches the subject I:

• me dejé = I left behind
• te dejaste = you left behind
• se dejó = he/she left behind

It is pronominal in form, but not truly reflexive in the literal English sense.

A literal reflexive idea would be something like I washed myself. But in me dejé el paraguas, the meaning is idiomatic: I accidentally left the umbrella behind.

So it is best to learn dejarse algo as a useful pattern:

• Me dejé las llaves en casa.
• Se dejó el móvil en el coche.

This is a very important difference.

• Me dejé el paraguas en la cafetería usually means I left my umbrella behind in the café — probably by mistake.
• Dejé el paraguas en la cafetería can sound more neutral or deliberate: I left the umbrella in the café.

So the version with me often suggests forgetting or accidentally leaving something behind.

Spanish very often uses the definite article with body parts, clothing, and personal belongings when ownership is obvious from the context.

So:

• Me dejé el paraguas = I left my umbrella behind

The sentence already tells us whose umbrella it is, because of me.

You can say mi paraguas, but it usually adds emphasis, contrast, or clarity:

• Me dejé mi paraguas, no el tuyo.

In normal conversation, el paraguas is the most natural choice.

Because the sentence refers to a completed action at a specific moment: you left the umbrella behind.

The preterite is used for single, finished events:

• Me dejé el paraguas en la cafetería.

The imperfect (me dejaba) would usually suggest a repeated or background action, so it would not fit this sentence well on its own.

Yes, that is understandable, but it is not exactly the same in feel.

• Me dejé el paraguas en la cafetería = I left my umbrella behind there.
• Olvidé el paraguas en la cafetería = I forgot the umbrella in the café.

In everyday Spanish, especially in Spain, me dejé... is very natural when talking about physically leaving an item somewhere by mistake.

So for keys, phones, bags, umbrellas, and similar objects, me dejé... is often the most idiomatic option.

It can correspond to either in or at in English, depending on how you would naturally translate it.

Spanish en is broader than English in. Here it simply gives the location where the umbrella was left:

• en la cafetería = in / at the café or cafeteria

English chooses whichever sounds more natural in context.

No. In Spanish, the verb ending already shows the subject.

• dejé = I left
• so yo is unnecessary in most cases

You would only add yo for emphasis, contrast, or clarification:

• Yo me dejé el paraguas, no tú.

The normal sentence is simply:

• Me dejé el paraguas en la cafetería.

The accent mark shows that the stress falls on the last syllable: de-JÉ.

It also helps distinguish this form from deje, which is a different verb form:

• dejé = I left
• deje = subjunctive / formal command form

So the accent is important both for pronunciation and grammar.

Yes. Me dejé + object + place is very natural and common in Spain when talking about things you accidentally left somewhere.

Examples:

• Me dejé las llaves en casa.
• Me dejé el móvil en el coche.
• Me dejé la cartera en el bar.

A learner who wants natural Spain Spanish should definitely get used to this structure.

Yes, very often. It is especially common with everyday personal items.

For example:

• Me dejé las gafas en la oficina.
• Me dejé el bolso en el restaurante.
• Me dejé la chaqueta en casa de Ana.

It works best when talking about something you left behind by mistake.

Not always.

In Spain, cafetería often means a café or casual place where you can have coffee, drinks, and food. It does not always mean a school or office cafeteria in the English sense.

So in this sentence, many learners would naturally translate cafetería as café, depending on the context.