Here is the text you can use for "dsl-3788 firmware" depending on where you need it (e.g., search query, forum post, or documentation).
Do not touch anything. The router will:
Despite its capable hardware, the DSL-3788 relies heavily on optimized firmware to handle the high throughput of modern VDSL connections. If the firmware is buggy or corrupt, the router may fail to synchronize with the ISP’s exchange equipment, resulting in the dreaded "red DSL light." dsl-3788 firmware
D-Link DSL-3788 Wireless AC1200 Gigabit VDSL2 Modem Router Here is the text you can use for