Staram się dbać o sen, a ona dba o rośliny na balkonie tak dobrze, że nawet zimą wyglądają dobrze.

Staram się means I try or I am trying.

It comes from the verb starać się = to try / to make an effort.
This verb normally includes się, so you learn it as a whole unit:

• starać się = to try
• staram się = I try
• stara się = he/she tries

In other words, się is not optional here. It is part of the verb.

After starać się, Polish commonly uses an infinitive, just like English does after try:

• Staram się dbać o sen = I try to take care of my sleep
• Staram się więcej czytać = I try to read more

So the structure is:

• staram się + infinitive

Here, the infinitive is dbać.

Dbać o means to take care of, to care for, or to look after.

Examples:

• dbać o zdrowie = to take care of one’s health
• dbać o dzieci = to look after the children
• dbać o rośliny = to care for plants

It is very important to learn it with o:

• dbać o kogoś/coś = to care for someone/something

So in your sentence:

• dbać o sen = care about / take care of sleep
• dba o rośliny = she takes care of the plants

Because dbać o takes the accusative case.

So:

• sen is the accusative form of sen
• rośliny is the accusative plural of roślina

Compare:

• nominative: sen
• accusative: sen

and

• nominative singular: roślina
• accusative singular: roślinę
• nominative plural: rośliny
• accusative plural: rośliny

In the plural, rośliny looks the same in nominative and accusative, which is very common for non-masculine-personal nouns.

Both are possible in some contexts, but they are not exactly the same.

• sen = sleep, the state/quality of sleep
• spanie = sleeping, the activity/process

So dbać o sen usually sounds more natural when talking about sleep as something important for health and rest.

For example:

• Dbam o sen = I take care of my sleep / I prioritize good sleep
• Spanie would sound more like the act itself

So sen is the better choice here.

Because dbać by itself is not a reflexive verb.

• starać się includes się
• dbać does not

So:

• Staram się = I try
• Ona dba = she takes care

You should think of them as two different verbs with different patterns:

• starać się + infinitive
• dbać o + accusative

Because na balkonie means on the balcony in the sense of location.

After na, Polish can use different cases depending on meaning:

• na + accusative = movement toward a place
  
  • Idę na balkon = I’m going onto the balcony
• na + locative = location
  
  • Rośliny są na balkonie = The plants are on the balcony

Here the plants are located there, so Polish uses the locative:

• balkon → na balkonie

Here a connects two clauses and contrasts them lightly:

• Staram się dbać o sen, a ona dba o rośliny...

It is not exactly the same as English and, and not as strong as but.
It often means something like:

• and meanwhile
• while
• whereas

So here it gives a natural comparison:

• I try to take care of sleep, while she takes care of the plants...

Tak dobrze, że... means so well that...

It is a very common Polish structure:

• tak + adverb/adjective + że
• so + adverb/adjective + that

Examples:

• Mówi tak szybko, że nic nie rozumiem.
  = He speaks so fast that I understand nothing.
• Dba o rośliny tak dobrze, że nawet zimą wyglądają dobrze.
  = She takes care of the plants so well that they look good even in winter.

So że introduces the result.

Because the two instances of dobrze describe different things.

1. dba ... tak dobrze
   Here dobrze describes how she takes care of them:

   • she cares for them well

2. wyglądają dobrze
   Here dobrze describes how the plants look:

   • they look good

So even though it is the same word, it has two separate jobs in the sentence.

Because the subject is rośliny = plants, which is plural.

So the verb must also be plural:

• roślina wygląda = the plant looks
• rośliny wyglądają = the plants look

The plural ending -ają is typical for many verbs in the 3rd person plural.

Zimą is a common adverbial form meaning in winter or during the winter.

It is historically the instrumental form of zima.

So:

• zima = winter
• zimą = in winter

Polish often uses seasons this way:

• latem = in summer
• zimą = in winter
• wiosną = in spring
• jesienią = in autumn

You can also hear w zimie, but zimą is very natural and concise.

Yes, very often.

Polish verb endings usually show who the subject is, so pronouns are often dropped unless you want emphasis or contrast.

This sentence could be shortened to:

• Staram się dbać o sen, a dba o rośliny na balkonie tak dobrze, że nawet zimą wyglądają dobrze.

But because there are two different people involved, keeping ona makes the contrast clearer.

Similarly, ja is not needed because staram się already means I try.

Yes, it is understandable and natural enough, especially in a health/lifestyle context.

It suggests:

• trying to maintain good sleep habits
• making sleep a priority
• taking care of one’s sleep quality

Depending on context, a Polish speaker might also say:

• Staram się dbać o zdrowy sen.
• Staram się wysypiać. = I try to get enough sleep.
• Dbam o sen. = I take care of my sleep.

But your sentence is perfectly fine.

Dbać is imperfective.

That makes sense because the sentence describes:

• an ongoing habit
• repeated care
• a general practice

She is not doing one single completed action. She regularly cares for the plants.

Likewise:

• starać się is also imperfective
• wyglądać is imperfective too

This fits the general meaning of repeated effort and ongoing results.

It breaks down like this:

• Staram się dbać o sen
  = I try to take care of my sleep

• a ona dba o rośliny na balkonie
  = and/while she takes care of the plants on the balcony

• tak dobrze, że
  = so well that

• nawet zimą wyglądają dobrze
  = even in winter they look good

So the full pattern is:

[Clause 1], a [Clause 2] tak dobrze, że [result clause].

That is a very useful pattern in Polish.