Bu dilde bolca pratik yaparsan, senin yazdığın cümleler hem doğal hem de kolay anlaşılır hale gelir.

Senin yazdığın cümleler means “the sentences that you write.” The phrase is constructed by combining:
• Senin – the possessive pronoun “your.”
• Yazdığın – a relative clause derived from the verb yazmak (to write) by adding a suffix that indicates “that you write.”
• Cümleler – the plural form of “sentence.”

In Turkish, relative clauses are appended directly to the noun without the need for a separate relative pronoun, resulting in a compact expression that conveys “the sentences you write.”

The expression hem doğal hem de kolay anlaşılır hale gelir translates to “become both natural and easy to understand.” It comprises two main parts:
• Hem... hem de... – a correlative construction used to tie together two qualities, equivalent to “both... and...” in English.
• Hale gelir – a phrase that literally means “comes to a state,” effectively meaning “becomes.”

Thus, the sentence conveys that if you practice a lot in this language, your written sentences will transform (or “become”) into ones that are natural in style and easy for others to understand.