Gölün kenarında çay içiyorum.

Because Turkish is showing a relationship like the edge of the lake.

Here, gölün is göl + -ün:

• göl = lake
• -ün = the genitive ending, roughly like of the or 's

So gölün kenarı literally means the lake's edge or the edge of the lake.

The form -ün appears because of vowel harmony. After ö, the genitive suffix becomes -ün.

Kenarında can be broken down like this:

• kenar = edge, side
• -ı = its / third-person possessive
• -n- = a linking consonant
• -da = in / on / at

So:

kenar-ı-n-da
= at its edge
= at the edge of it

Since it refers back to the lake, gölün kenarında means at the lake's edge or by the lake.

This is a very common Turkish pattern called a genitive–possessive construction.

In English, we usually say:

• the edge of the lake
• the lake's edge

In Turkish, both parts are marked:

• the possessor gets the genitive: gölün
• the possessed thing gets a possessive ending: kenarı

So the core pattern is:

göl-ün kenar-ı
= lake-GEN edge-its
= the edge of the lake

Then -da is added to mean at/on/in, giving kenarında.

Both can often be translated similarly, but there is a nuance.

• gölün kenarında = at the edge of the lake, often sounding more explicitly like a possessed phrase
• göl kenarında = by the lakeside or at the lake shore, more like a fixed compound

So:

• gölün kenarında can feel more like at the edge of that specific lake
• göl kenarında can feel a bit more general or lexicalized, like lakeside

In everyday speech, both are natural, and the difference is often small.

Because çay here is an indefinite / non-specific direct object.

In Turkish:

• çay içiyorum = I am drinking tea / I'm having tea
• çayı içiyorum = I am drinking the tea / that tea

The accusative ending -ı / -i / -u / -ü is usually used when the object is specific or definite.

So in this sentence, çay is just tea in a general sense, not the tea.

İçiyorum breaks down like this:

• iç- = drink
• -iyor = present continuous / progressive
• -um = I

So:

içiyorum = I am drinking

This is the normal way to talk about an action happening now. In this sentence, it means the speaker is currently drinking tea.

Because Turkish verbs already show the person.

In içiyorum, the ending -um tells you the subject is I.

So ben is not necessary:

• çay içiyorum = I am drinking tea

You can add ben if you want emphasis:

• Ben gölün kenarında çay içiyorum = I am drinking tea by the lake / As for me, I'm drinking tea by the lake

Turkish often leaves subject pronouns out unless they are needed for emphasis or contrast.

Not completely. Turkish word order is flexible, although the verb usually comes last.

This sentence has:

• Gölün kenarında = place
• çay = object
• içiyorum = verb

So the structure is very natural: place + object + verb.

You could also say:

• Çay içiyorum gölün kenarında

That is still understandable, but it sounds different in emphasis. Putting gölün kenarında first highlights the setting: by the lake.

Turkish does not have a separate word exactly like English the.

And although bir can sometimes mean a / an, it is not always required.

So:

• çay içiyorum = I am drinking tea
• bir çay içiyorum = I am drinking a tea / I'm having a tea

Likewise, definiteness is often understood from context rather than from an article.

The main ones here are:

• ö in gölün: a rounded front vowel, similar to German ö or French eu
• ü in gölün: similar to German ü or French u
• ç in çay: like ch in chair
• ı in kenarında: a sound English does not really have; it is a plain, unrounded vowel pronounced farther back than i

A rough pronunciation guide:

• gölün ≈ guh-lün but with rounded vowels
• kenarında ≈ keh-nah-ruh(n)-duh
• çay ≈ chai
• içiyorum ≈ ee-chee-yo-rum

Not perfect English approximations, but good enough to get started.