The covenant which I will make (ἡ διαθήκη ἣν δοαθήσομαι)
The noun and the verb are cognate - the arrangement which I will arrange. A covenant (διαθήκη) is something arranged (διατίθεσθαι) between two parties. See the same combination, Act 3:25.
I will put my laws (διδοὺς νόμους μου)
Lit. giving my laws: const. with I will make: “the covenant which I will make by giving my laws.”
Mind (διάνοιαν)
The moral understanding. See on Mar 12:30; see on Luk 1:51. Hearts, καρδίας, see on Rom 1:21; see on Rom 10:10.
A God - a people (εἰς θεόν - εἰς λαόν)
Lit. unto a God, etc. A Hebraistic form of expression, εἰς signifying the destination of the substantive verb. The sense is, I will be to them to serve as a God; or my being as related to them will amount to my being a God to them. Comp. Mat 19:5; 2Co 6:18; Heb 1:5.