how generate  part of scriptSig in bitcoin transactions I studied many links about bitcoin trxs and about generating scriptSig.
Finally I couldn't understand how to make this part.

for example I read this links:

What is relation between scriptSig and scriptPubKey?

https://bitcoin.org/en/developer-guide#transactions

How do you create a scriptsig for a new raw tx?

How to redeem a basic Tx?

How to create the &lt;sig&gt; &lt;PubK&gt; part in &quot;scriptSig&quot;?

http://www.righto.com/2014/02/bitcoins-hard-way-using-raw-bitcoin.html

https://en.bitcoin.it/wiki/Protocol_documentation#tx

https://en.bitcoin.it/wiki/Transaction

I found that I must sign a thing but whats that thing ?

exactly and step by step What should I put together and then sign it?

specially if I had more than 1 input how make sigscript ?

I have a library that does the sign operation for me. however, I don't know what structure I need to use for the message that is going to be signed especially when there are multiple outputs.
The data to be signed is called Hash Preimage. Then you sign the double SHA256 of hash preimage, which is 256-bits long. Before hashing, the data must be formed as shown in this answer. If you're signing a SegWit transaction, the contents of the preimage changes, as defined in BIP 143.

Then you can use the formulae here, Eq. 2:

(x1, y1) = k × G(x, y) mod p
r = x1 mod n


k is a random number, G is the generator, p is the prime modulo, etc.

Then,

s = (k^-1 (h(m) + d * r)) mod n


d is the private key, h(m) is the double SHA256 result. Now, you can use r, s to create the DER-encoded signature.