Этот чемодан весит почти двадцать килограммов, поэтому мне трудно поднять его на полку.

Because чемодан is a masculine singular noun, and the demonstrative this has to agree with it:

• этот = masculine singular
• эта = feminine singular
• это = neuter singular

So этот чемодан means this suitcase.

It is in the nominative singular because it is the subject of the verb весит:

• Этот чемодан весит... = This suitcase weighs...

The subject of the sentence is normally in the nominative.

Весить is the dictionary form (the infinitive), meaning to weigh.

In the sentence, we need the present-tense, 3rd person singular form because the subject is этот чемодан:

• весить = to weigh
• он весит = it weighs

So:

• Этот чемодан весит почти двадцать килограммов = This suitcase weighs almost twenty kilograms

After numbers like 5, 6, 7... 20, Russian normally uses the genitive plural form of the noun.

So:

• двадцать килограммов = twenty kilograms

This is part of the standard number pattern in Russian:

• 1 килограмм
• 2 / 3 / 4 килограмма
• 5+ килограммов

Since двадцать belongs to the 5+ group, you get килограммов.

Sometimes yes, especially with units of measure in certain styles, but for a learner, килограммов is the safest and most standard form here.

So in this sentence, почти двадцать килограммов is the form you should expect and use.

Поэтому means therefore, so, or that’s why.

It connects the two parts of the sentence:

• Этот чемодан весит почти двадцать килограммов
• поэтому мне трудно поднять его на полку

The comma is used because Russian is joining two clauses, roughly like:

• This suitcase weighs almost twenty kilograms, so it’s hard for me to lift it onto the shelf.

Russian often uses an impersonal construction for feelings or difficulty:

• мне трудно = it is difficult for me
• literally: to me [it is] difficult

Here мне is the dative case of я.

This pattern is very common:

• мне легко = it’s easy for me
• мне трудно = it’s hard for me
• мне интересно = it’s interesting to me

So мне трудно поднять его means it is difficult for me to lift it.

Поднять is perfective, and поднимать is imperfective.

Here the speaker means one specific completed action: lifting the suitcase up onto the shelf. That is why поднять is natural.

• поднять = to lift, to raise, to pick up successfully/completely
• поднимать = to be lifting, to lift repeatedly, or to talk about the action in a more general/process sense

So:

• мне трудно поднять его на полку = it’s hard for me to lift it onto the shelf

If you used поднимать, it would sound more like a general or repeated activity.

Его means him or it, depending on context. Here it means it, referring back to чемодан.

In the sentence, его is the direct object of поднять:

• поднять его = to lift it

So the structure is:

• мне трудно поднять его = it is hard for me to lift it

Because Russian uses different cases depending on whether you mean movement toward a place or location in a place.

With на:

• на полку = onto the shelf → accusative, because there is movement
• на полке = on the shelf → prepositional, because it describes location

Here the suitcase is being moved onto the shelf, so Russian uses:

• на полку

It most directly means lift it onto the shelf.

The verb поднять focuses on the physical act of raising/lifting something upward. That fits well here because the suitcase is heavy.

If the speaker wanted to focus more on the final placement, Russian might use a different verb, such as положить in some contexts. But here the emphasis is clearly on the effort of lifting.

Yes. Russian word order is much more flexible than English word order.

This sentence could be rearranged in various ways, for example:

• Этот чемодан весит почти двадцать килограммов, поэтому мне трудно поднять его на полку.
• Мне трудно поднять этот чемодан на полку, потому что он весит почти двадцать килограммов.

The original order sounds natural and clear. It first mentions the suitcase and its weight, then gives the result: therefore it’s hard for me to lift it onto the shelf.

The main stresses are:

• Э́тот
• чемода́н
• ве́сит
• почти́
• два́дцать
• килогра́ммов
• поэ́тому
• мне́
• тру́дно
• подня́ть
• его́
• на по́лку

So the full sentence is pronounced approximately as:

Э́тот чемода́н ве́сит почти́ два́дцать килогра́ммов, поэ́тому мне́ тру́дно подня́ть его́ на по́лку.

This is useful because Russian stress is not always predictable, especially in words like чемодан, поэтому, and килограммов.