Be careful with this company. After complete delivery of the files agreed in the contract and aproved as complete by this company, Lingvohouse wanted 3 weeks after the delivery deadline was passed and the contract was already completely fulfilled extra files that were never included in the contract and wrote they do not pay me when I do not send these in addition.

Although this was not my duty I delivered these additional files just to get my money.

And then they claimed the additional delivered stuff outside the contract was not okay. But I could prove with screenshots and videos that they are working okay and are complete. But they still did not pay.

After making them clear together with a lawyer the legal consequences for them if not paying me, they suddenly paid me only to avoid a lawsuit for copyright infringement.

It cost lots of nerves and time to run after the money after the work was done.

I recommend:
Do NOT any work for them after 100% PRE-PAYMENT.
You could have the same experience.

UPDATE:
dear Lingvohouse, your reply does hide the following:
1) I was forced to deliver additional files which were never included in the contract!

2) I was not paid for this extra-work!
My lawyer said clearly this extra work outside our contract needs to be paid by you in addition and I can send an invoice for this, too - of course!

3) Not forgetting to mention that you (Lingvohouse) have clauses in your contract that are against the law like 15% deduction of payment per hour of late delivery!
I do have proofs for this as everything was saved by me with witnesses.

4) The money was only paid after a lawyer was involved as the files were already used although Lingvohouse had no copyrights on them!

5) the due date was not 26th as Lingvohouse wanted to pay at the 6th (20 DAYS EARLIER) written by email in the garantee sent from the CEO when I deliver the extra files outside the contract, what I did on the agreed time although I never had the duty to deliver these extra files that were never included in the contract.
But Lingvohouse did not keep this agreement and did not pay. So a lawyer had to be involved to make them pay!

And not to forget: Lingvohouse forced me to deliver these extra files outside the contract mentioning they won't pay me when I do not deliver these file. What this legaly means: every lawyer will tell you!

6) it is not allowed to force a freelancer to deliver extra work / files
3 weeks after the delivery deadline was passed and the contractual agreed files were already approved to be complete and the contract was already fulfilled.

So forcing a freelancer to deliver extra files outside the contract by saying not to pay when he does not deliver these extra files and even without paying for this extra work is against the law!
This business behavior can be reported to the Competition and Markets Authority UK.
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Just to make this clear! Be aware!
ONLY work for them after 100% PRE-PAYMENT or you need a lawyer to be involved to get your money!