Could you correct this?

messier42Is this sentence correct?

It's rather obscure.

Since the second quarter, the time to complete the installations has run anywhere from 20 to 40 days. The normal installation time is only 15 days. (So we are not meeting our schedule...)

The installation completion have been running from 20 to 40 days, failing the required installation time, 15 days, to be met since quarter 2. How about this?

messier42 The installation completion have been running from 20 to 40 days, failing the required installation time, 15 days, to be met since quarter 2. How about this?

No, it is not grammatically correct and it would be difficult for someone to understand.

I was trying to make one sentence including all information. Could you do it?

Since the second quarter, the time to complete the installations, which normally is limited to 15 days, has run anywhere from 20 to 40 days.

I don't understand why you are restricted to a single sentence. Writing clearly often is best accomplished with succinct sentences, each with a main point. This is especially important in business communications.

There was a form which requires just one sentence as a tittle.

A title, like a headline, does not need to be a complete sentence. Often fragments are used, or extraneous words omitted.
Are you sure you needed a headline?