I want Firmware for router Huawei HG531S V1 ...

Hello,
Here is the enterprise forum,
For mobile & home device issue, pls refer to:
Support: http://consumer.huawei.com/en/
You are also welcome to send an email to mobile@mail01.huawei.com or dial the hotline number （https://consumer.huawei.com/en/support/hotline/） if you have any questions about Huawei Consumer products.
Thanks for your understanding.

Hello, I have found the enterprise series products( https://support.huawei.com/enterprise/en/category/access-network-pid-1482605784817?submodel=9856746)
and carrier series products( https://support.huawei.com/carrier/navi?coltype=product#col=product&path=PBI1-7275726/PBI1-7275738). I do not have your model. I think your device belongs to the local carrier's customized device. I suggest you contact your carrier or device vendor to obtain the firmware.

Good luck!