Fiance visa, financial details & other issues

Im looking to apply for a fiancé visa for my gf. She currently lives in Germany but is divorced & has all the paperwork, she is a Thai national.

My query relates mainly to the financial details that need to be submitted with the application. How long should bank statements date back, the same for wage details and is there anything specific my employer should say within his letter above and beyond how long I have worked there and my salary?

We have been in a relationship for nearly 4 years and continue to meet every 10 weeks or so, however when we talk (which is every night) its via Skype or other social media rather than emails. will this be an issue as I cannot produce copies of recent emails.

Many thanks in advance.

Assuming that you're Welsh, then see also specified evidence requirements.

Can you provide Skype records?

thanks for the link, ive read it before and got confused so i'll re-read it.

as Skype is video I don't think I can provide records

You should have a Skype record of calls made/received, video or not.