If your expenses are genuinely 13k then of course it's not too much, how could it be? As long as you have a record of what you've spent, and you're confident you're only claiming for business use, you'll be fine.

If you're doing self-assessment you only need to declare overall profit anyway, not turnover, not at that level.

What "invoice"/proof you need to have for advertisement expenses?
And other question what to do with aw advertisement? Like I pay 20pm for local escort featuring and like 32x4 or 5 for escort featuring. But this comes from my income there and I do not put money in.

You'll need the receipt to your email if you paid online, or the physical receipt if you paid in cash.

With AW if I withdraw credits then I declare that as income at the date it hits my bank account, I only count as an expense if I've bought credits. I usually do enough on webcam and gallery/movie sales to not have to load credits.

Are you filing self assessment, or going through an accountant?

If you're doing it yourself, you just need to keep all your receipts and income records, for use in the unlikely event that you get audited. During self assessment you are simply asked for your overall profit for the year. You are not asked for a breakdown of income and expenditure when filing online.

If you're using an accountant, just give them all the receipts and ask them what they suggest you declare as the nature of your business.

Ok, but then it's doomed? Let's say you are saying you are message therapist and then you need to show that you paid for ad for escorting site? Will they check everything, will they say to change your employement information? What else can happen?

Can accountant be claimed as expenses? Lol