ok so I've attempted to translate the first sentence for now. I know there are probably errors, so if you could point them out, I'd greatly appreciate that.
Nos Maczko Borkowicz palatinus Posnaniensis, universis et singulis harum rerum serie notum fore volumus : quod licet lege ac natura humana persuadentibus et exigentibus quilibet homo domino suo praesertim principi fidelis obediens et obsequiosus esse debeat et teneatur, tunc tamen ad ea multomagis est astrictus et obligatus, quando ipsa facere promittens juramento et literis patentibus roborat et confirmat. Idcirco inhaerentes vestigiis nostrorum parentum et praedecessorum, quorum fidelitas clarissimis principibus Poloniae piae recordationis, utpote propriis dominis grata fuit, et accepta, maginifico principi domino nostro Casimiro, Dei gratia regi Poloniae, sicut alias juravimus et promissimus omnem fidelitatem et totalem, ita et per praesentes absque specie omnis fraudis et doli volumus et promittimus, et prout de jure teneamur, debemus praestito corporali juramento servitia fidelia quaelibet et obsequia pro suo regio honore, commodo et utillitate suo regni et reipublicae facere, exhibere, totoque desiderio pure ac sincere adimplere harum testimonio literarum, quibus nostrum sigillum est appensum. Actum et datum Syradiae, feria sexta post diem Cinerum, anno millesimo trecentesimo quinquagesimo octavo.
We, Maczko Borkowicz, Palatine of Poznań, want it to be known to each and all by the succession of these things that although any man, especially to a prince, ought to be faithful, obedient, and complying to his master, as law and human nature convinces and requires, and to belong to him, he nevertheless is then much more bound and obligated to those things when[ever] he strengthens and confirms to observe these very duties by promising through an oath and a written document.
