Article in English: Norfolk Island pines like moist soil, but they don't do well with excessive watering. If the branches become limp or start turning yellow, water the tree less often.  The tree only needs to be watered when the top inch (2.5 cm) of soil becomes dry. The yellow needles may also drop if you're overwatering. Yellowing needles (not accompanied by limp branches) can be a sign that you aren't giving the tree enough water. Water the soil thoroughly when it dries out, and provide the tree with additional humidity. You can increase the humidity by misting the tree daily. Watch out for the lower branches turning brown and dropping off especially. This is a telltale sign that the tree isn't getting enough light. Move the tree closer to a northeast or northwest window, a shaded south or west window, or to a solarium.  Norfolk Island pines need lots of indirect sunlight. If you cannot provide the tree with enough natural light, consider using a full-spectrum bulb that's designed for plants. Dropping needles that don't change color can be a sign of a few things, including too much or too little moisture. Often, it's an indication of too little moisture. If the soil feels dry and you don't water often, water the tree more frequently. If the soil is damp and you water often, cut back. Dropping needles can also indicate that the tree is too close to a draft.

Summary in Vietnamese:
Giảm tưới nước nếu các cành cây rũ xuống và úa vàng. Điều chỉnh cách tưới nếu lá cây chuyển vàng. Cung cấp thêm ánh sáng cho cây nếu các cành dưới thấp chuyển màu nâu. Điều chỉnh độ ẩm nếu lá cây rũ xuống.