"I am reading a book next to the lamp."
Translation:Lambanın yanında bir kitap okuyorum.
You missed an important detail: this change of consonants only happens when words (not just nouns) are ending on certain consonants. İt is applied on words ending on k, t, ç, p (memorized by the word ketçap). The changes are k -> ğ, t -> d, ç -> c, p -> b. Examples: tavuk -> tavuğu, kağıt -> kağıdı, ilaç -> ilacı, kitap -> kitabı. Finally, you just didn't spell lamba correctly :)
This is because there is a secret genitive construction in here. In Turkish, to say "next to," you really have to say something that is literally like "at the X's side" :)
yan = side lamba = lamp
Lambanın yanında = next to the lamp
For what it's worth, lambası = his/her lamp
Please see Alex's comment above.
This "genitive construction" (putting the possessive suffix at the end of the word) happens for all of these ways of describing the location of something (next to, inside, on top of, etc.). The tips and notes section for the postposition skill is helpful for knowing how and when to use the "possessive" suffix.
"I am reading a book next to the lamp." Translation: Lambanın yanında bir kitap okuyorum.
Lamba (noun) -> "lamp" + consonant buffer (n) + -ın -> Lambanın -> genitive case, "possessor."
What is, "possessed?" -> yan + -ı possessive suffix + consonant buffer (n) + -da locative suffix.
Lambanın yanı -> "the side of the lamp."
Subject (Lambanın yanında) object (a book) verb (okumak)
Okumak (verb) -> detach -mak + -yor present tense personal ending + -um 1st person singular possessive suffix.
Okuyorum -> "I am reading."
Example for "yan" -> side.
"Yüzüme bakamadın yan yana iken."
Both dative case suffixes, "to" my face & "to" a side.
Yan yana iken -> side by side for a while/when.