Ta ramka jest lżejsza niż tamten obraz, więc jeden hak powinien wystarczyć.

Because ramka is a feminine noun in Polish, and the demonstrative this must agree with the noun’s gender.

• ten = this/that for masculine
• ta = this/that for feminine
• to = this/that for neuter

So:

• ta ramka = this frame

The noun ramka ends in -a, which is very often a sign that a noun is feminine.

Usually, yes. Ramka means frame, especially a small frame or picture frame.

It is related to rama, which means frame in a more basic sense.
Ramka is a very common form and often feels natural when talking about a picture frame, photo frame, or a small frame.

So in this sentence, ta ramka most likely means:

• this frame
• possibly this picture frame

Lżejsza is the comparative form of lekka / lekki, meaning lighter.

The basic adjective is:

• lekki = light (masculine)
• lekka = light (feminine)
• lekkie = light (neuter)

The comparative is irregular-looking:

• lżejszy = lighter (masculine)
• lżejsza = lighter (feminine)
• lżejsze = lighter (neuter)

Since ramka is feminine, the adjective must agree with it:

• ta ramka jest lżejsza = this frame is lighter

So the -a ending is there because the thing being described, ramka, is feminine.

Yes. This works very much like English:

• X jest lżejszy niż Y = X is lighter than Y

So:

• Ta ramka jest lżejsza niż tamten obraz
  = This frame is lighter than that painting/picture

Using jest here is completely normal.

Yes. Niż means than in comparisons.

Examples:

• większy niż = bigger than
• tańszy niż = cheaper than
• lżejsza niż = lighter than

So:

• lżejsza niż tamten obraz = lighter than that painting

Polish also sometimes uses od with the genitive in comparisons, but niż is very common and straightforward.

For example:

• Ta ramka jest lżejsza niż tamten obraz.
• Ta ramka jest lżejsza od tamtego obrazu.

Both can mean the same thing.

Tamten means that and agrees with obraz.

The noun obraz is masculine singular, so the demonstrative must also be masculine singular:

• ten obraz = this picture/painting
• tamten obraz = that picture/painting

This is the same agreement pattern as with ta ramka:

• feminine noun → ta
• masculine noun → tamten here, because it means that

It can mean several related things, depending on context:

• painting
• picture
• image

In everyday contexts, obraz often means a painting or a framed picture on a wall.
Since the sentence also mentions a hook, that wall-hanging idea fits well.

So in this sentence, tamten obraz is probably best understood as:

• that painting
• or that picture

Więc means so, therefore, or thus.

It connects the two parts of the sentence logically:

• The frame is lighter than that painting, so one hook should be enough.

So here więc introduces the conclusion:

• lighter object → probably needs less support → one hook should be enough

Jeden means one.

Polish does not always need to state one, just like English sometimes says a hook instead of one hook. But here jeden emphasizes the number:

• jeden hak = one hook

That makes sense because the sentence is about whether a single hook is enough.

Also, hak is a masculine noun, so jeden appears in the masculine form.

Because powinien agrees with the subject, which is jeden hak.

• hak is masculine
• so the form is powinien

Compare:

• hak powinien wystarczyć = the hook should be enough
• ramka powinna wystarczyć = the frame should be enough
• krzesło powinno wystarczyć = the chair should be enough

So the gender of powinien / powinna / powinno depends on the noun it refers to.

This is a very common Polish structure:

• powinien = should
• wystarczyć = to be enough / to suffice

So:

• jeden hak powinien wystarczyć
  literally: one hook should suffice

This is similar to English should + verb:

• should work
• should help
• should be enough

In Polish, after powinien, you typically use the infinitive:

• powinien wystarczyć
• powinien działać
• powinien pomóc

Because after powinien, Polish uses the infinitive.

So:

• jeden hak wystarczy = one hook is enough / will be enough
• jeden hak powinien wystarczyć = one hook should be enough

The second one is less direct and expresses expectation or likelihood.

So the difference is:

• wystarczy = finite verb form
• wystarczyć = infinitive

Wystarczyć means to be enough, to suffice, or to be sufficient.

Examples:

• To wystarczy. = That’s enough.
• Jedna osoba wystarczy. = One person is enough.
• Powinno wystarczyć. = It should be enough.

In this sentence:

• jeden hak powinien wystarczyć = one hook should be enough

The word order is very natural and neutral.

• Ta ramka jest lżejsza niż tamten obraz, więc jeden hak powinien wystarczyć.

Polish word order is more flexible than English, but this version sounds standard and clear.

The sentence is built like this:

1. Ta ramka — the topic
2. jest lżejsza niż tamten obraz — comparison
3. więc — logical connector
4. jeden hak powinien wystarczyć — conclusion

You could rearrange parts in Polish for emphasis, but this version is probably the most normal one for a learner to copy.

It would be:

• Ta ramka jest lżejsza od tamtego obrazu, więc jeden hak powinien wystarczyć.

Notice the change:

• niż tamten obraz
• od tamtego obrazu

After od, the noun phrase changes case, here to the genitive:

• tamten obraz → tamtego obrazu

Both versions are correct.
For many learners, niż feels easier at first because the noun stays in the form you expect more easily.

Yes, it can look tricky.

lżejsza is pronounced approximately like:

• lzhey-sha

A few notes:

• ż sounds like the s in measure
• ej sounds roughly like ay in say
• sz sounds like sh

So the word has two Polish sounds English speakers often need practice with:

• ż
• sz

Even if pronunciation is not perfect at first, learners are usually understood if they aim for something close to lzhey-sha.