Can you please tell me if it is OK in the sentence:

During negotiation it is necessary to make sure that in return for our concessions we always get what is approximately close to that/their value, as well as not to accept what does not suit us or what we would never accept in more relaxed circumstances.

Thank you
'we always get'... Maybe 'we always obtain' if you want to be more formal ?

'that/their' I think it has to be 'their value'.

'... as well as not to...' I sense it should be constructed the same as the previous part, so '... as well as do not accept...' since it is intended to complement 'we always...' : we always get... and we always do not accept...
An alternative:

During negotiations we must ensure that we get a good return for our concessions. We must also reject anything that does not suit us, or that we would not accept in more favourable circumstances.

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Thank you Waiti for your suggestions, corrections and most important-your time.
 MrPedantic's reply was promoted to an answer.
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I find your post very helpful Mr Pedantic, thank you!