xìn / zhōng / bùbiàn / zhǎnkāi / shuōmíng / děng / nǐ / dǐdá / Běijīng / hòu / wǒmen / zài / miànxù

信中不便展开说明，等你抵达北京后，我们再面叙。

It is inconvenient to explain everything in the letter; we can discuss it face-to-face after you arrive in Beijing.