Tamen hodiaŭ ni devas ŝanĝi tiun kutimon, ĉar ni ne havas sufiĉe da tempo.

Tamen means however, nevertheless, or all the same.

In this sentence, tamen adds a contrast to something said earlier: even so, today we must change that habit...

A useful distinction is:

• sed = but; it directly links two contrasting ideas
• tamen = however / nevertheless; it works more like an adverb commenting on the whole statement

So:

• Sed often corresponds to English but
• Tamen often corresponds to English however / still / nevertheless

Esperanto can even use both together for extra contrast: Sed tamen...

Esperanto word order is fairly flexible. Hodiaŭ means today, and putting it after tamen is a natural way to organize the sentence:

• Tamen hodiaŭ ni devas...

This gives a flow like:

• However, today, we must...

You could move hodiaŭ to other places and still be understood, for example:

• Hodiaŭ tamen ni devas ŝanĝi tiun kutimon...
• Ni devas hodiaŭ ŝanĝi tiun kutimon...

But the original order sounds natural and emphasizes the contrast first (tamen) and then the time frame (hodiaŭ).

After modal verbs like devi (must / have to), Esperanto normally uses the infinitive form of the next verb.

So:

• devas = must / have to
• ŝanĝi = to change

Together:

• ni devas ŝanĝi = we must change

This is similar to English:

• we must change not
• we must changeS

Other common examples:

• mi volas iri = I want to go
• ili povas veni = they can come
• ŝi devas labori = she has to work

Because tiun kutimon is the direct object of ŝanĝi.

In Esperanto, the direct object takes -n. Also, words that go together must agree with each other.

Here:

• tiu = that
• kutimo = habit

As the direct object, both become accusative:

• tiun kutimon = that habit

This agreement is very important in Esperanto:

• tiu kutimo = that habit
• tiun kutimon = that habit (as direct object)

The same thing happens with adjectives:

• bona kutimo
• bonan kutimon

Because tiu already makes the noun definite.

In Esperanto, demonstratives like tiu (that) and ĉi tiu (this) normally replace la, rather than combining with it.

So you say:

• tiu kutimo = that habit

not:

• la tiu kutimo

This is much like English, where we say that habit, not the that habit.

Ĉar means because. It introduces the reason for what was said in the main clause.

So the structure is:

• ni devas ŝanĝi tiun kutimon = main statement
• ĉar ni ne havas sufiĉe da tempo = reason

In other words:

• We must change that habit, because we do not have enough time.

Unlike in some languages, the word order after ĉar stays normal:

• ĉar ni ne havas...

There is no special inversion.

Because the clause after ĉar is its own full clause, and it normally needs its own subject.

So:

• ĉar ni ne havas sufiĉe da tempo

literally has the same basic structure as any normal sentence:

• ni = subject
• ne havas = verb
• sufiĉe da tempo = object/quantity phrase

Even though English sometimes relies more heavily on context, Esperanto usually states the subject clearly when a new clause begins.

In Esperanto, ne normally comes directly before the word or phrase it negates.

Here it negates the verb:

• ni ne havas = we do not have

That is the standard pattern:

• mi ne scias = I do not know
• ili ne venos = they will not come
• ŝi ne povas resti = she cannot stay

If you move ne, you may change the emphasis or make the sentence unnatural.

This is a very common Esperanto quantity pattern.

• sufiĉe = enough
• da = a particle used after words of quantity
• tempo = time

So:

• sufiĉe da tempo = enough time

You can think of da as meaning something like of, but in Esperanto it is specifically used after quantity expressions:

• multe da akvo = a lot of water
• iom da mono = some money
• tro da laboro = too much work
• sufiĉe da tempo = enough time

This is one of the most important uses of da.

After da, the noun is usually left in its basic form, and with a mass noun like tempo, the singular is natural.

So:

• sufiĉe da tempo = enough time

not usually:

• sufiĉe da tempoj

That is because time here is being treated as an uncountable quantity, just like in English.

Compare:

• multe da akvo = a lot of water
• iom da sablo = some sand
• sufiĉe da tempo = enough time

If you were talking about separate countable items, plural might make sense, but not here.

Yes, that is possible, and it means roughly the same thing.

Compare:

• ni ne havas sufiĉe da tempo
• ni ne havas sufiĉan tempon

Both can mean we do not have enough time.

The difference is mainly one of structure:

• sufiĉe da tempo uses a quantity phrase
• sufiĉan tempon uses sufiĉa as an adjective modifying tempo

The da version is extremely common and often feels especially natural when talking about quantity.

Because ĉar ni ne havas sufiĉe da tempo is a subordinate clause giving a reason.

Esperanto punctuation is generally based on clarity, and a comma before ĉar is very common and natural:

• ..., ĉar ...

It helps the reader see the structure immediately:

• main clause first
• reason clause after it

You may notice that Esperanto punctuation can be a little flexible in some contexts, but here the comma is standard and helpful.

The main special sounds here are:

• ŝ = like English sh
  • ŝanĝi sounds roughly like SHAHN-jee / SHAHN-ghi, depending on accent
• ĉ = like English ch
  • ĉar sounds like char
• aŭ = a diphthong, roughly like ow in cow
  • hodiaŭ sounds approximately ho-DEE-ow

A few more useful notes:

• ĝ in ŝanĝi sounds like the j in jam
• ŭ is very short and gliding; it usually combines with a preceding vowel, as in aŭ

Esperanto pronunciation is very regular, so once you learn these letter sounds, you can read new words with confidence.