I have two wordpress website. One installed in main domain and another one installed in sub-domain under main domain. I'm doing this to manage 2 different language. I know there are so many plugins to manage multi language in site. But I have to do this manually.

But now i need to done a small job. I want to show a notification when any visitor will visit my main site for the 1st time. There I'll give 2 Language option to choose.

```
Option-1 Language English for main domain. (example.com)
Option-2 Language Spanish for Sub domain. (sp.example.com)

```

When visitor will select `Option-1` he will stay in `main site(domain)`. If he select `Option-2` then he will be redirected to the `another site(sub-domain)` and after this it'll happen automatically every time he visits 

main site(domain)
-----------------

. But visitor can manually come back to main domain from sub-domain. 

Any solution will be highly appreciated. Thanks