העכבר שלי לא עובד, אז אני משתמשת רק במקלדת עד סוף היום.

In modern Hebrew, when you use שלי / שלך / שלו and so on, the noun is usually written with the definite article ה־.

So:

• העכבר שלי = my mouse
• הבית שלי = my house

For an English speaker, this feels a little strange because Hebrew is basically saying something like the mouse of mine. Using the ה־ here is the normal modern pattern.

Yes. עכבר is used for both meanings.

Usually context makes it clear:

• ראיתי עכבר במטבח = I saw a mouse in the kitchen
• העכבר שלי לא עובד = my mouse isn’t working

Yes, and that is exactly why it is used here. In Hebrew, עובד is commonly used for machines, devices, apps, internet connections, and so on.

So:

• המחשב עובד = the computer works / is working
• האינטרנט לא עובד = the internet isn’t working
• העכבר לא עובד = the mouse doesn’t work

English also says my mouse isn’t working, so this matches pretty well.

Hebrew usually does not use a present-tense form of to be.

So:

• העכבר שלי לא עובד literally looks like my mouse not working
• אני משתמשת literally looks like I using

But in natural English, those mean:

• My mouse isn’t working / doesn’t work
• I am using

This is a very common feature of Hebrew.

משתמשת is the feminine singular present-tense form.

So:

• a woman says אני משתמשת
• a man says אני משתמש

In Hebrew present tense, verbs agree with the gender and number of the subject.

The dictionary form is להשתמש = to use.

A very important point: להשתמש normally goes with ב־ before the thing being used.

For example:

• להשתמש במקלדת = to use a keyboard / the keyboard
• להשתמש בטלפון = to use a phone / the phone
• להשתמש במחשב = to use a computer / the computer

So Hebrew does not say משתמשת מקלדת. It needs the ב־.

Because Hebrew prepositions like ב־ are usually attached directly to the following word.

So:

• ב + מקלדת becomes במקלדת

Also, if there is a definite article ה־, then ב + ה contracts:

• ב + המקלדת becomes במקלדת in normal unpointed spelling

That means במקלדת can represent:

• with a keyboard
• with the keyboard

The spelling is the same; context tells you which is meant.

Yes, very often it can.

Hebrew speakers often say:

• אז משתמשת רק במקלדת עד סוף היום

But אני is still perfectly natural. It can make the sentence clearer, slightly more explicit, or just sound better in context.

Because רק usually goes right before the part it limits or focuses on.

Here:

• משתמשת רק במקלדת = using only the keyboard

So the idea is:

• not the mouse
• just the keyboard

If you move רק, the emphasis can change.

Here אז means so, therefore, or then.

It connects the two parts:

• my mouse doesn’t work
• so I’m using only the keyboard

It is a very common everyday linking word.

It means until the end of the day.

Breakdown:

• עד = until
• סוף = end
• היום = the day / today, depending on context

סוף היום is a construct phrase, literally end of the day. Hebrew often expresses of relationships this way, without a separate word for of.

So:

• עד סוף היום = until the end of the day / until the end of today

Yes, Hebrew word order is somewhat flexible.

For example, these are all possible:

• אז אני משתמשת רק במקלדת עד סוף היום
• אז אני רק משתמשת במקלדת עד סוף היום
• עד סוף היום אני משתמשת רק במקלדת

They are not identical in emphasis, but they are all understandable. The original version is very natural and straightforward.